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CURRENT FROM THE MAIN.
1571 fatal
cases were
those of effusion
on
the
left side-this is very
would fail to
register
any of this
leakage.
The
following
interesting, and confirms the belief held by some that left- diagramswill serve to illustrate the electrical conditions .sided pleuro-pneumonia is always more dangerous to life than that exist-for example, in a bath-when an earth connexion when it occurs on the right ; (2) in all there was a long is made. history of illness before admission, varying from six weeks ,to three months; (3) in one gangrene of the lung was believed to exist, but this could not be proved post mortem ; 4) of the two deaths occurring in children under two years of age, one was the direct sequence of chicken-pox, and in both the children were rachitic to a degree ; and (5) one ,case suffered from thrombosis of the left iliac vein six days .after operation, and he died on the eighth day. The deductions I would draw from these facts are as follows: (1) that free incision when done early is very successful; (2) that the removal of a portion of a rib is never necessary in acute cases ; and (3) that a fatal issue at "any age is rather the result of the neglect to recognise the Arue nature of the case, than from the operation itself. Nottingham.
CURRENT FROM THE MAIN. BY W. S. HEDLEY, M.D. EDIN.,
There is one "series" R = 80 and there are two parallel branches (R = 600 + 2 + 10 and R = 1). Then the total 612 x 1 resistance = + 80 = 80998’ and the total current 6172 +-l1
MEDICAL OFFICES IN CHARGE OF THE ELECTRO-THERAPEUTIC DEPARTMENT OF THE LONDON HOSPITAL.
Si-NcE the publication under the above heading of two .,rticles on the utilisation of public supply currents for 1420 m.a. Of this total the body will take an - electro-therapeutic purposesgreat progress has been made average of 25 per cent.,’-that is, it will receive 355 m.a. ’in the supply of electricity from central stations. The same The current in the respective parallel branches will be as interval has brought forth a variety of apparatus as well as 612 : 1-in other words, the milliampere meter will register 2’3 m.a. Had the patient been placed in contact with the ,, somewhat extensive literature bearing upon the points in wire and the resistance been interposed uninsulated .question ; but it cannot be said that by any writer has there between him(neutral) and the insulated pole (positive or negative) he yet been shown a complete grasp of the subject, nor by any would not, even if placed in an uninsulated bath, have been instrument have the many serious difficulties of the case ever in the circuit of any earth current. This would hold good only ’been adequately met. In view, however, of the great and so long as the condition of the mains was good. Should a fault ’increasing employment of these currents, and with an break out on one of the outer wires (positive or negative) the state of affairs would be in no way different from the experience of their usefulness in medicine, the time seems case just considered. What, then, is the remedy for this risk ? 4o have arrived for a complete survey of the whole problem ; insulation. It should be taken as an axiom that Clearly .and the following remarks offer themselves as an attempt at the current from public supply mains should -7M<’’ be applied ’iits solution. either as a shunt or direct to the patient without interposing Considering the improvement that has taken place in between him and the earth an insulating substance of such a public supply currents, I am of opinion that for medical i nature as would undoubtedly stand the full main pressure ’employment their chief danger now lies, not in the possible across it without passing a current of 1 m.a. In the case of influx of strong currents or in the chances of a failure of three wire systems the "full main pressure " would be double supply, but in leakage currents and in the breakdown of that of supply, and in five wire systems four times that of transformers, and of these risks the greater is leakage. supply. This necessity for insulation would apply equally to 1. Leakage currents.-This source of danger has hitherto all systems, whether continuous or alternating, direct or been either under-estimated or completely ignored, but it is transformed. In the usual electrical applications security ’nevertheless a very serious one, and in the absence of suit- would be attained by standing on a very dry floor or, more able precautions may lead to accidents of a grave kind. certainly, on a varnished kamptulicon mat. But in the case "Those stations which supply by direct distribution, or of the water bath, connecting as it does with a good earthing distribution from transforming centres, are undoubtedly, device in the shape of waste pipes and water pipes, the case ’and for obvious reasons, more subject to earth leakage than is altogether different, and certain additional precautions then become necessary. With these duly carried out effective .are those in which transformers are used at or near the house. Again, stations supplying electricity on the three insulation can certainly be secured. In the first place it is or five wire systems, even if they do not actually obvious that the bath should not be made of metal. Hard connect to an earth plate or water pipe, are likely to have wood or porcelain are suitable materials, the latter by preferthe middle wire (theneutral") at practically earthence. The bath should stand upon glass mushroom insulators {potential. It is true that any connexion to earth of a main Jfilled with a heavy resinous oil (similar to those used for insupplying current direct to houses is forbidden by the BoardI sulating storage batteries) or it might be placed upon hard ’of Trade, but when, for purposes of its own, it suits a vulcanised rubber blocks. The inlet stopcocks for both hot company to earth its middle wire this regulation does not and cold water should be placed some distance from the seem to bar the practice. Now, if under these circumstances bath, and in such a position that it would be impossible for the patient be placed in contact with one of the outer mains the patient, when in the bath, to accidentally make contact (positive or negative) what may be expected to happen ? If with them. An insulating piece of porcelain or vulcanised ’the connexion to earth be good, even a damp floor, such a rubber should be inserted in both inlet pipes between the stoppatient would be subjected to the full pressure of supply, cocks and the bath. If the waste pipe be attached to the bath usually 100 volts or more. It is obvious that if the contact an insulating piece should be inserted as close to the bath as be of low resistance (for instance, if the patient be in an possible. But danger may be even more easily and effectually uninsulated bath) the resultant current through the patient’s averted by fixing directly below the waste outlet of the bath .body might be one of considerable and even dangerous 2 These diagrams are only intended to show by an example the magnitude, perhaps approaching 400 milliamperes. It would possible danger to a patient from leakage currents. 115 volts is the full be useless to interpose resistance between the patient and pressure of the mains. The total current under the above conditions ’the uninsulated (neutral) pole, as this portion of the circuit is 1420 m.a., and the resistance in the respective branches is 612 ohms would be shunted by the leakage current, and if the milli- and lohm, and, as current is inversely proportional to resistance, the circuit) will .ampere meter was also placed in this portion of the circuit it current in the circuit of high resistance (the galvanometer both circuits
(00) 80v998
be 2·3 m.a., and in the earth circuit 1417·7
1 Current from the Main. By W. S. Hedley, M.D., THE Dec. 19th, 1891, and April 9th, 1892.
LANCET,
common to the bath. 3 most recent
My
a
conclusion in
m.a.
But
are
experiments, shortly to be published, prove thisstartling contrast with former surmises.
.1572 ii shallow tank or sink to receive waste water from the bath, fix upon each pole of the electro-therapeutic circuit a, r the waste pipe being attached to this sink. Neither the tank reliable magnetic cut-out. The best apparatus of this kincil nor the waste pipe should make contact with the bath. i that known ns the "Cunynghame," of which the following is I havejust read, and not without misgiving, the report of a is i a description. Two planished ends of a copper solenoid’ discussion at the recent conferenoe of the Board of Trade (dip into two mercury cups forming the terminals of the upon the question of raising the limit of low-pressure supply, iinstrument, and on the current reaching a predetermined It cannot be said that on this occasion the calculations of ,amount the solenoid is "sucked over" (drawn back upon) a, the commercial electrical engineer were hampered by anyIcurved, soft, iron core-piece, the position of which is fixedl undue regard for the safety of human life. It was claimed but adjustable. The solenoid is fastened to one end of a, by several of those present that they had received harmless radialarm which is pivot,ed at its lower end in such a way shocks from what are now considered to be high-pressure that a slight movement of the solenoid brings it vertically circuits. One gentleman asserted that lie had felt no ill over the turning captre and into a position of unstable effects from a 600 volt shock. In view of the fact that so equilibrium; any further increase of current will cause the’ milch depends upon contact and the manner of taking a solenoid to drop by force of gravity and at the same timeshock, and that little or no information was given on this withdraw the contact points from the mercury cup, thus’ point, it is difficult to form an opinion from such a state- breaking the circuit. If desired, the mercury cup could be meat. Did the gentleman in question touch one pole only of short-circuited by a resistance of such an amonnt as would’ a ?0 volt circuit ? If so, what was the earth insulation of reduce the current in the circuit to half or quarter of the the other pole ? Was his body in contact with the earth?I breaking current. For example, let it be supposed that the Or, presuming that he simultaneously placed one hand on magnetic cut-out has been set to break circuit at 200m.a.,. each pole of the 600 volt circuit, what was the surface area of and that the electromotive force of supply is 100 volts, there skin contact, and what the condition of the skin’1 In the the resistance to the circuit must be = 500 ohms. Now,. absence of information on these points the statement referred ’200 to cannot be considered to have any real value. Ilad the if the magnetic cut-out be short-circuited with a resistance. surface area and condition of the skin been favourable for a of 500 ohms, the current, instead of ceasing altogether, low resistance contact, it is more than possible that the 100 m.a. ; or, if been " put to would be diminished to aUU + bUU gentleman in question might ere tins earth " in a .ense other than an electrical one. 1500 ohms be used as a short-circuiting resistance, the2. Brea7,(Io?vib of traii,fori)ie7-s.-The second source of 50 m.a,. danger (one which, of course, can occur only with trans- current would have been diminished to formed systems) is that due to the breakdown of the Where two magnetic cut-outs (one on each pole) are used it insulation between the primary and secondary windings of would be well to short-circuit both instruments with resistThis risk does not belong exclusively to a transformer. and to set one to act a little in advance of the ances, alternating current systems. Continuous current trans- other. Fusible cut-outs and lamps in the circuit haveformers are now used in several public installations, notably been recommended as safeguards, but it has been moreat Oxford (1000 volts primary) and at Chelsea (500 volts than once pointed out by me in THE IjAKCET that at primary). In the event of a breakdown of the insulation the best such devices are unreliable for the purpose in question secondary mains would have their potential above earth very and may lead to the serious discomfiture of those who put considerably raised, and should it happen that there are their trust in them. It is well known that fuses cannot be weak places in the network of secondary (distributing) to act within 5 per cent, of their nominal current;. mains (of which the patient’s body, unless well insulated guaranteed it is necessary also to remember that even then they take from earth, would form one) an exccssive current would quite an appreciable time to heat and melt. Again, the pass, with probably fatal results to the patient. The Board difficulty of obtaining small fuses of reliable gauge is greater of Trade regulations provide that every secondary circuit of than with fuses of larger capacity. With lamps the result is a high-pressure main shall be fitted with an approved form even more uncertain. The resistance of carbon diminishes of apparatus for automatically connecting the secondary as the filament grows hot until the state of incandescence is mains to earth in the event of their potential above earth reached, after which resistance remains practically constant. rising to a dangerous degree : but in this case there is the Again, the temperature to which it is raised under normal. not improbable contingency that when the occasion for conditions depends entirely upon the efficiency lighting its action arises such an apparatus will be out of order, per candle) at which the lamp is intended to burn;: and, even if it be working well, it cannot act until (watts therefore it is evident that as a fuse a lamp’s breaking the potential above earth of the mains has risen to must With high-efficiency lamps-i.e., this dangerous degree. And after that there is still an with vary considerably. which absorb small voltage for candle-power-lamps interval, short but quite appreciable, required for the the ratio between the nominal current and the fusing current action of the device in question. It must be borne in will be less than with low-efficiency lamps. Used as a, mind that during this time the excessive potential is acting as a choking or current-reducing resistance—i.e., "backing" upon the patient unless he be very well insulated, and, resistance of steady value-a lamp to ensure anything tikefurther, that it does not take long, with good contacts, to reliability should have a considerable current passed through kill a man with 1000 or 2000 volts. What, then, are the it-certainly full incandescence should be attained. Ar. precautionary measures here’?’I Never to rely solely upon safeguards, therefore, for electro-therapeutic purposes fusiblethe insulation of the patient from earth when the supply is cut-outs and lamps are entirely out of the question. a transformed one, but always to place a substantially made cleared the ground of the only serious difficulties Having transformer in the circuit. With alternating currents a that lie in the way of utilising lighting currents, I hope;, , " " transformer Woakes or 11 Miller and ’W oods may be to go on to consider their physical characters, their thera-used ; but it should be tested with at least the pressure of peutic qualities, and the control apparatus by which suchthe primary mains between its primary and secondary currents may be best adapted to the varied requirements or windings before being installed for work. With continuous practice. currents from a transformed system it will be well to interpose a motor, and make this drive by belt a small dynamo which should not be fixed on the same metal bed-plate. The dangers due to leakage and the breakdown of the transformer A CONTRIBUTION TO THE SURGICAL TREATMENT OF MALIGNANT DISEASE represent practically the whole of the difliculties that have to be contended with so far as the company’s mains are conOF THE BREAST. cerned. The risks of failure of supply and serious rise of supply pressure need not, in the case of English companies BY ROBERT SANDERSON, M.B. OXON., M.R.C.S. ENG., at least, now be seriously considered. The companies for LATE DEMONSTRATOR OF ANATOMY, WESTMINSTER HOSPITAL MEDICAL. SCHOOL ; SURGEON TO THE WOMEN’S HOSPITAL, BRIGHTON. their own sakes take every possible precaution to guard against these accidents, and usually with complete THE published statistics of the results of the surgical success. Under any circumstances it is desirable to treatment of malignant disease of the breast so plainly show 4 This instrument has on one bobbin three separate secondary coils ; disappointing results that little apology seems to be demanded one supplies cautery, the second light, and the third gives current for an attempt either to criticise the past or make suggestions. to the patient. application 5 This device is provided with a number of terminals on the secondary for the future. It has become an acknowledged principle of’ winding, such that any voltage from 2 upwards and any current up to the treatment that not only should the whole affected mamma 20 ampères can be obtained.
a
100
have
100/500+500 = 100/500+1500 =
I
point
for
cases were
those of effusion
on
the
left side-this is very
would fail to
register
any of this
leakage.
The
following
interesting, and confirms the belief held by some that left- diagramswill serve to illustrate the electrical conditions .sided pleuro-pneumonia is always more dangerous to life than that exist-for example, in a bath-when an earth connexion when it occurs on the right ; (2) in all there was a long is made. history of illness before admission, varying from six weeks ,to three months; (3) in one gangrene of the lung was believed to exist, but this could not be proved post mortem ; 4) of the two deaths occurring in children under two years of age, one was the direct sequence of chicken-pox, and in both the children were rachitic to a degree ; and (5) one ,case suffered from thrombosis of the left iliac vein six days .after operation, and he died on the eighth day. The deductions I would draw from these facts are as follows: (1) that free incision when done early is very successful; (2) that the removal of a portion of a rib is never necessary in acute cases ; and (3) that a fatal issue at "any age is rather the result of the neglect to recognise the Arue nature of the case, than from the operation itself. Nottingham.
CURRENT FROM THE MAIN. BY W. S. HEDLEY, M.D. EDIN.,
There is one "series" R = 80 and there are two parallel branches (R = 600 + 2 + 10 and R = 1). Then the total 612 x 1 resistance = + 80 = 80998’ and the total current 6172 +-l1
MEDICAL OFFICES IN CHARGE OF THE ELECTRO-THERAPEUTIC DEPARTMENT OF THE LONDON HOSPITAL.
Si-NcE the publication under the above heading of two .,rticles on the utilisation of public supply currents for 1420 m.a. Of this total the body will take an - electro-therapeutic purposesgreat progress has been made average of 25 per cent.,’-that is, it will receive 355 m.a. ’in the supply of electricity from central stations. The same The current in the respective parallel branches will be as interval has brought forth a variety of apparatus as well as 612 : 1-in other words, the milliampere meter will register 2’3 m.a. Had the patient been placed in contact with the ,, somewhat extensive literature bearing upon the points in wire and the resistance been interposed uninsulated .question ; but it cannot be said that by any writer has there between him(neutral) and the insulated pole (positive or negative) he yet been shown a complete grasp of the subject, nor by any would not, even if placed in an uninsulated bath, have been instrument have the many serious difficulties of the case ever in the circuit of any earth current. This would hold good only ’been adequately met. In view, however, of the great and so long as the condition of the mains was good. Should a fault ’increasing employment of these currents, and with an break out on one of the outer wires (positive or negative) the state of affairs would be in no way different from the experience of their usefulness in medicine, the time seems case just considered. What, then, is the remedy for this risk ? 4o have arrived for a complete survey of the whole problem ; insulation. It should be taken as an axiom that Clearly .and the following remarks offer themselves as an attempt at the current from public supply mains should -7M<’’ be applied ’iits solution. either as a shunt or direct to the patient without interposing Considering the improvement that has taken place in between him and the earth an insulating substance of such a public supply currents, I am of opinion that for medical i nature as would undoubtedly stand the full main pressure ’employment their chief danger now lies, not in the possible across it without passing a current of 1 m.a. In the case of influx of strong currents or in the chances of a failure of three wire systems the "full main pressure " would be double supply, but in leakage currents and in the breakdown of that of supply, and in five wire systems four times that of transformers, and of these risks the greater is leakage. supply. This necessity for insulation would apply equally to 1. Leakage currents.-This source of danger has hitherto all systems, whether continuous or alternating, direct or been either under-estimated or completely ignored, but it is transformed. In the usual electrical applications security ’nevertheless a very serious one, and in the absence of suit- would be attained by standing on a very dry floor or, more able precautions may lead to accidents of a grave kind. certainly, on a varnished kamptulicon mat. But in the case "Those stations which supply by direct distribution, or of the water bath, connecting as it does with a good earthing distribution from transforming centres, are undoubtedly, device in the shape of waste pipes and water pipes, the case ’and for obvious reasons, more subject to earth leakage than is altogether different, and certain additional precautions then become necessary. With these duly carried out effective .are those in which transformers are used at or near the house. Again, stations supplying electricity on the three insulation can certainly be secured. In the first place it is or five wire systems, even if they do not actually obvious that the bath should not be made of metal. Hard connect to an earth plate or water pipe, are likely to have wood or porcelain are suitable materials, the latter by preferthe middle wire (theneutral") at practically earthence. The bath should stand upon glass mushroom insulators {potential. It is true that any connexion to earth of a main Jfilled with a heavy resinous oil (similar to those used for insupplying current direct to houses is forbidden by the BoardI sulating storage batteries) or it might be placed upon hard ’of Trade, but when, for purposes of its own, it suits a vulcanised rubber blocks. The inlet stopcocks for both hot company to earth its middle wire this regulation does not and cold water should be placed some distance from the seem to bar the practice. Now, if under these circumstances bath, and in such a position that it would be impossible for the patient be placed in contact with one of the outer mains the patient, when in the bath, to accidentally make contact (positive or negative) what may be expected to happen ? If with them. An insulating piece of porcelain or vulcanised ’the connexion to earth be good, even a damp floor, such a rubber should be inserted in both inlet pipes between the stoppatient would be subjected to the full pressure of supply, cocks and the bath. If the waste pipe be attached to the bath usually 100 volts or more. It is obvious that if the contact an insulating piece should be inserted as close to the bath as be of low resistance (for instance, if the patient be in an possible. But danger may be even more easily and effectually uninsulated bath) the resultant current through the patient’s averted by fixing directly below the waste outlet of the bath .body might be one of considerable and even dangerous 2 These diagrams are only intended to show by an example the magnitude, perhaps approaching 400 milliamperes. It would possible danger to a patient from leakage currents. 115 volts is the full be useless to interpose resistance between the patient and pressure of the mains. The total current under the above conditions ’the uninsulated (neutral) pole, as this portion of the circuit is 1420 m.a., and the resistance in the respective branches is 612 ohms would be shunted by the leakage current, and if the milli- and lohm, and, as current is inversely proportional to resistance, the circuit) will .ampere meter was also placed in this portion of the circuit it current in the circuit of high resistance (the galvanometer both circuits
(00) 80v998
be 2·3 m.a., and in the earth circuit 1417·7
1 Current from the Main. By W. S. Hedley, M.D., THE Dec. 19th, 1891, and April 9th, 1892.
LANCET,
common to the bath. 3 most recent
My
a
conclusion in
m.a.
But
are
experiments, shortly to be published, prove thisstartling contrast with former surmises.
.1572 ii shallow tank or sink to receive waste water from the bath, fix upon each pole of the electro-therapeutic circuit a, r the waste pipe being attached to this sink. Neither the tank reliable magnetic cut-out. The best apparatus of this kincil nor the waste pipe should make contact with the bath. i that known ns the "Cunynghame," of which the following is I havejust read, and not without misgiving, the report of a is i a description. Two planished ends of a copper solenoid’ discussion at the recent conferenoe of the Board of Trade (dip into two mercury cups forming the terminals of the upon the question of raising the limit of low-pressure supply, iinstrument, and on the current reaching a predetermined It cannot be said that on this occasion the calculations of ,amount the solenoid is "sucked over" (drawn back upon) a, the commercial electrical engineer were hampered by anyIcurved, soft, iron core-piece, the position of which is fixedl undue regard for the safety of human life. It was claimed but adjustable. The solenoid is fastened to one end of a, by several of those present that they had received harmless radialarm which is pivot,ed at its lower end in such a way shocks from what are now considered to be high-pressure that a slight movement of the solenoid brings it vertically circuits. One gentleman asserted that lie had felt no ill over the turning captre and into a position of unstable effects from a 600 volt shock. In view of the fact that so equilibrium; any further increase of current will cause the’ milch depends upon contact and the manner of taking a solenoid to drop by force of gravity and at the same timeshock, and that little or no information was given on this withdraw the contact points from the mercury cup, thus’ point, it is difficult to form an opinion from such a state- breaking the circuit. If desired, the mercury cup could be meat. Did the gentleman in question touch one pole only of short-circuited by a resistance of such an amonnt as would’ a ?0 volt circuit ? If so, what was the earth insulation of reduce the current in the circuit to half or quarter of the the other pole ? Was his body in contact with the earth?I breaking current. For example, let it be supposed that the Or, presuming that he simultaneously placed one hand on magnetic cut-out has been set to break circuit at 200m.a.,. each pole of the 600 volt circuit, what was the surface area of and that the electromotive force of supply is 100 volts, there skin contact, and what the condition of the skin’1 In the the resistance to the circuit must be = 500 ohms. Now,. absence of information on these points the statement referred ’200 to cannot be considered to have any real value. Ilad the if the magnetic cut-out be short-circuited with a resistance. surface area and condition of the skin been favourable for a of 500 ohms, the current, instead of ceasing altogether, low resistance contact, it is more than possible that the 100 m.a. ; or, if been " put to would be diminished to aUU + bUU gentleman in question might ere tins earth " in a .ense other than an electrical one. 1500 ohms be used as a short-circuiting resistance, the2. Brea7,(Io?vib of traii,fori)ie7-s.-The second source of 50 m.a,. danger (one which, of course, can occur only with trans- current would have been diminished to formed systems) is that due to the breakdown of the Where two magnetic cut-outs (one on each pole) are used it insulation between the primary and secondary windings of would be well to short-circuit both instruments with resistThis risk does not belong exclusively to a transformer. and to set one to act a little in advance of the ances, alternating current systems. Continuous current trans- other. Fusible cut-outs and lamps in the circuit haveformers are now used in several public installations, notably been recommended as safeguards, but it has been moreat Oxford (1000 volts primary) and at Chelsea (500 volts than once pointed out by me in THE IjAKCET that at primary). In the event of a breakdown of the insulation the best such devices are unreliable for the purpose in question secondary mains would have their potential above earth very and may lead to the serious discomfiture of those who put considerably raised, and should it happen that there are their trust in them. It is well known that fuses cannot be weak places in the network of secondary (distributing) to act within 5 per cent, of their nominal current;. mains (of which the patient’s body, unless well insulated guaranteed it is necessary also to remember that even then they take from earth, would form one) an exccssive current would quite an appreciable time to heat and melt. Again, the pass, with probably fatal results to the patient. The Board difficulty of obtaining small fuses of reliable gauge is greater of Trade regulations provide that every secondary circuit of than with fuses of larger capacity. With lamps the result is a high-pressure main shall be fitted with an approved form even more uncertain. The resistance of carbon diminishes of apparatus for automatically connecting the secondary as the filament grows hot until the state of incandescence is mains to earth in the event of their potential above earth reached, after which resistance remains practically constant. rising to a dangerous degree : but in this case there is the Again, the temperature to which it is raised under normal. not improbable contingency that when the occasion for conditions depends entirely upon the efficiency lighting its action arises such an apparatus will be out of order, per candle) at which the lamp is intended to burn;: and, even if it be working well, it cannot act until (watts therefore it is evident that as a fuse a lamp’s breaking the potential above earth of the mains has risen to must With high-efficiency lamps-i.e., this dangerous degree. And after that there is still an with vary considerably. which absorb small voltage for candle-power-lamps interval, short but quite appreciable, required for the the ratio between the nominal current and the fusing current action of the device in question. It must be borne in will be less than with low-efficiency lamps. Used as a, mind that during this time the excessive potential is acting as a choking or current-reducing resistance—i.e., "backing" upon the patient unless he be very well insulated, and, resistance of steady value-a lamp to ensure anything tikefurther, that it does not take long, with good contacts, to reliability should have a considerable current passed through kill a man with 1000 or 2000 volts. What, then, are the it-certainly full incandescence should be attained. Ar. precautionary measures here’?’I Never to rely solely upon safeguards, therefore, for electro-therapeutic purposes fusiblethe insulation of the patient from earth when the supply is cut-outs and lamps are entirely out of the question. a transformed one, but always to place a substantially made cleared the ground of the only serious difficulties Having transformer in the circuit. With alternating currents a that lie in the way of utilising lighting currents, I hope;, , " " transformer Woakes or 11 Miller and ’W oods may be to go on to consider their physical characters, their thera-used ; but it should be tested with at least the pressure of peutic qualities, and the control apparatus by which suchthe primary mains between its primary and secondary currents may be best adapted to the varied requirements or windings before being installed for work. With continuous practice. currents from a transformed system it will be well to interpose a motor, and make this drive by belt a small dynamo which should not be fixed on the same metal bed-plate. The dangers due to leakage and the breakdown of the transformer A CONTRIBUTION TO THE SURGICAL TREATMENT OF MALIGNANT DISEASE represent practically the whole of the difliculties that have to be contended with so far as the company’s mains are conOF THE BREAST. cerned. The risks of failure of supply and serious rise of supply pressure need not, in the case of English companies BY ROBERT SANDERSON, M.B. OXON., M.R.C.S. ENG., at least, now be seriously considered. The companies for LATE DEMONSTRATOR OF ANATOMY, WESTMINSTER HOSPITAL MEDICAL. SCHOOL ; SURGEON TO THE WOMEN’S HOSPITAL, BRIGHTON. their own sakes take every possible precaution to guard against these accidents, and usually with complete THE published statistics of the results of the surgical success. Under any circumstances it is desirable to treatment of malignant disease of the breast so plainly show 4 This instrument has on one bobbin three separate secondary coils ; disappointing results that little apology seems to be demanded one supplies cautery, the second light, and the third gives current for an attempt either to criticise the past or make suggestions. to the patient. application 5 This device is provided with a number of terminals on the secondary for the future. It has become an acknowledged principle of’ winding, such that any voltage from 2 upwards and any current up to the treatment that not only should the whole affected mamma 20 ampères can be obtained.
a
100
have
100/500+500 = 100/500+1500 =
I
point
for