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RESISTANCE TO KETOSIS IN OBESE SUBJECTS
1157
injected " ketone " was distributed throughout the total body water within a few minutes of injection. The highest concentrations obtained were almost identical in
RESISTANCE TO KETOSIS IN OBESE SUBJECTS A. KEKWICK M.A., M.B. Cantab., F.R.C.P.
all 12 subjects. The
rate
of decline of the blood-levels in
PROFESSOR OF MEDICINE
G. L. S. PAWAN B.Sc. Lond. RESEARCH BIOCHEMIST
T. M. CHALMERS M.D. Edin., M.R.C.P. FIRST ASSISTANT
THE DEPARTMENT OF
MIDDLESEX HOSPITAL MEDICAL
MEDICINE,
SCHOOL, LONDON, W.1
IT has long been recognised that fat people do not readily develop ketosis (Duncan 1959, Kekwick and Pawan 1957). This study was undertaken to try to elucidate the mechanism underlying their resistance. The level of ketone bodies in the blood (acetone, acetoacetic acid, and p-hydroxybutyric acid) depends on the balance between their rate of production by the liver and their rate of utilisation and excretion. Two possible explanations therefore presented themselves: (1) that
the obese could utilise or excrete ketone bodies faster than the non-obese, and thus prevent them accumulating
Fig. 2-Blood " ketonesafter intravenous injection of 60 sodium 0-hydroxybutyrate per kg. body-weight.
mg.
the two groups was similar, suggesting that they utilised the sodium B-hydroxybutyrate at about the same rate. Fig. 2 shows the blood values obtained when twice the above dose was given to 2 obese and 2 non-obese subjects. No difference between the two groups could be seen even when higher initial blood-ketone levels were obtained. Table I shows the amount of ketone bodies recovered in the urine from 5 of the obese subjects and 7 of the nonobese. The striking feature of these figures is the small amount recovered (less than 1% of the dose given). Stadie (1958) and Campbell and Best (1956) have pointed out that isolated organs and intact animals can utilise ketone bodies readily and that probably almost all tissues of the body have this property. The small proportion of the dose recovered here suggests that this is equally true of human subjects, whether obese or non-obese. The two groups,
however, excreted comparable
after intravenous injection of 30 Fig. I-Blood " ketones sodium B-hydroxybutyrate per kg. body-weight. "
mg.
in the body; (2) that the obese did not form ketone bodies so rapidly. To test the first hypothesis sodium B-hydroxybutyrate was given to 6 obese and 6 non-obese subjects. In each the dose was calculated in proportion to body-weight and was administered intravenously (30 mg. of sodium B-hydroxybutyrate per kg. body-weight). As in previous papers (Kekwick and Pawan 1956), the obese were defined as those who had such an obvious excess of subcutaneous fat that no doubt could be entertained in any observer’s mind that they were too fat. The non-obese were selected by a similar criterion: they were manifestly thin. Fig. 1 shows the blood values obtained after injection. The values for " total ketones " are expressed as milligrammes of acetone per 100 ml. of blood and were measured by the method previously published (Pawan 1958).* Recalculating the concentrations obtained in terms of sodium The estimation
it
preceded by oxidation of with acid dichromate.
was
to acetoacetate
B-hydroxybutyrate,
seems
that the
(3-hydroxybutyrate
amounts in the urine. Hence the first hypothesis-that the resistance to ketosis in the obese results from their greater ability to excrete ketone bodies or to utilise them metabolicallydoes not appear to be tenable. An attempt to induce ketosis was next made in 14 obese and 8 non-obese subjects by giving them a diet providing 1000 calories, of which 90% was supplied in the form of fat (Kekwick and Pawan 1956). The criterion of nonobesity in this group was not so rigidly applied as in the first experiment, for we were anxious to discover whether TABLE I-URINARY KETONES EXCRETED DURING VENOUS
INJECTION
OF SODIUM
5
HOURS AFTER INTRA-
B-HYDROXYBUTYRATE
1158 fall in the fasting blood-sugar concentration-a fall which is much less evident in the obese. It can be further noted that this fall took place mainly on the first and second days after starting the diet. Fig. 3 shows that in most subjects the rise in blood ketones took place on or after the second day of the dietary period and was on the whole consequent upon the appearance of hypoglycasmia. The daily carbohydrate intake of the two groups was identical, and amounted to only 12 g. This is clearly less than the daily requirements for both. An obvious possible source of additional carbohydrate Fig. 3-Rise in blood "ketones " in subjects on a 1000-calorie 90%-fat diet. was from body protein, and nitrogen balances were therefore carried out in both those who might wish to reduce weight for cosmetic groups during the dietary period. From fig. 5 it is clear that the non-obese were in negative nitrogen balance reasons were liable to ketosis on a high-fat diet. None of the lean subjects, however, would have been treated as whereas the obese were almost in nitrogen equilibrium. obese patients for medical reasons. TABLE II-FASTING BLOOD-SUGAR LEVELS IN SUBJECTS ON A The relative resistance to ketosis in the obese was con1000-CALORIE 90 "o-FAT DIET firmed. All the obese subjects were able to take the diet for as long as required, whereas 7 of the 8 non-obese subjects had to abandon the diet by the fifth day, and the remaining subject on the eighth day, because of symptoms attributed to ketosis (headaches, anorexia, nausea, &c.). The development of symptoms in different individuals, however, did not appear to be closely related to the height of the blood-ketone levels. Fig. 3 shows the rate of rise in blood ketones in the two groups, and it can be seen that the obese had a slower rise in blood ketones than the non-obese. Fig. 4 shows the output of urinary ketones in the two groups. As might be expected, the amount excreted was much greater in the non-obese. In studies of post-exercise ketosis, Johnson and Passmore (1959) have pointed out that the rate of excretion of acetoacetate is related in a linear manner to the blood concentration, while the excretion of -hydroxybutyrate is exponentially related to blood concentration. Taken in conjunction with the first experiments, these results suggest that resistance to ketosis in the obese results from a diminished production of ketone bodies. It is usually thought that ketone bodies are formed only in the liver (Campbell and Best 1956, Stadie 1958) and of The non-obesehad an average nitrogen balance of -86g. that their rate of formation depends on the values were recorded in both a day as opposed to —l-5g.in the obese; representing a carbohydrates. Blood-sugar the that in Table II shows dietary period. groups during daily breakdown of about 54 g. and 10 g. of protein of the non-obese all but 2 subjects there was a significant respectively. Thus the extra carbohydrate available to the obese could not have come from nitro-
availability
" ketones " (ketone bodies estimated 1000-calorie 90""-fat diet.
Fig. 4-Output of subjects
on a
as
acetone) in the urine in
genous sources. A simple calculation can now be made in respect of the carbohydrate available in the two groups. It is clear (table ill, lines 1, 2, and 3) that in both of them the carbohydrate from the diet or body proteins is far below the minimal daily requirements. It is generally accepted that the human brain utilises carbohydrate as its principal source of energy (Lambertsen et,al. 1953). Blood leaving the brain has a respiratory quotient of 0-97 and the rate of utilisation of oxygen is 5-25 ml. per minute. The needs of the brain alone are therefore of the order of 75 g. glucose a day. Such a figure
1159 4. In non-obese people given a high-fat diet the developketonsemia and ketosis was preceded by a fall in the fasting blood-sugar concentration. In obese people on this diet, there was no such fall or it was small; and they did not develop ketosis to any significant degree. 5. Reasons are given for believing that net conversion of fat to carbohydrate took place in both groups. It is suggested that obese people may be able to turn fat into carbohydrate at a higher rate than non-obese people.
ment of
Fig. 5-Nitrogen balances in subjects for 4-14 days.
on a
1000-calorie 90%-fat diet
is almost certainly on the low side. Doubtless other organs also require some carbohydrate for their normal metabolism. Table in, lines 4 and 5, extends this calculation to show that neither group of subjects was getting enough carbohydrate to supply even the brain alone with its daily needs, and that the apparent deficit in the obese group was much the greater. Both groups therefore must have obtained carbohydrate from some other source, and it is our belief they could obtain it only from fat.Such a conclusion is by no means new (Lyon et al. 1932). The evidence both for and against the possibility is summed up by Weinman et al. (1957). They conclude that it is still uncertain whether conversion of fat to carbohydrate with a net gain in carbohydrate can take place in man; but it is difficult to escape the conclusion that it must have happened in these
We should like to thank Miss E. Wilkinson Hughes, principal dietitian, Middlesex Hospital; Miss M. Clode for biochemical help; Miss C. M. Evans for secretarial assistance; and two ward sisters, Miss R. S. Starkey and Miss J. Ward. REFERENCES
-
subjects. clear that in man the minimal daily needs for carbohydrate lie between 75 g. a day (the amount necessary for brain metabolism) and 400 g. a day (the normal carbohydrate intake). There is, however, no evidence that the daily needs are the same for the two groups studied here. The minimal needs may well be less in the obese because It
seems
TABLE
III-SUMMARY OF DAILY CARBOHYDRATE BALANCES NON-OBESE AND OBESE GROUPS ON 90%-FAT DIET
IN
THE
other sources of energy, such as fatty acids, can be more readily used by the tissues. If this is not so, the data suggest that obese people can produce more carbohydrate from non-protein sources (i.e., from fat).
Summary 1. It is much more difficult to induce ketosis in obese than in non-obese people. 2. The difference does not appear to depend on a higher rate of utilisation or excretion of ketone bodies by the obese. After intravenous injection of sodium &bgr;-hydroxybutyrate the rate of disappearance of this ketone body from the blood was found to be the same in obese as in non-obese people. Less than 1 % of the injected dose was excreted in the urine: the amount excreted was the same in the two groups. 3. Presumably, then, the rate of production of ketone bodies is less in the obese.
t
S. B. Furnass
(unpublished data) has found twenty-four-hour protein respiratory quotients around 0-7 in obese subjects 1000-calorie 90%-fat diet.
nonon a
Campbell, J., Best, C. H. (1956) Metabolism, 5, 95. Duncan, G. G. (1959) Diseases of Metabolism. Philadelphia. Johnson, R. E., Passmore, R. (1959) J. Physiol. 146, 51P. Kekwick, A., Pawan, G. L. S. (1956) Lancet, ii, 155. (1957) Metabolism, 6, 447. Lambertsen, C. J., Kough, R. H., Cooper, D. Y., Emmel, G. L., Loeschcke, H. H., Schmidt, C. F. (1953) J. appl. Physiol. 5, 471. Lyon, D. M., Dunlop, D. M., Stewart, C. P. (1932) Biochem. J. 26, 1107. Pawan, G. L. S. (1958) ibid. 68, 33P. Stadie, W. C. (1958) Diabetes, 7, 173. Weinman, E. O., Strisower, E. H., Chaikoff, I. L. (1957) Physiol. Rev. 37, 252. —
—
CONTROL OF ANTICOAGULANT THERAPY A TRIAL OF THROMBOTEST
J. M. MATTHEWS M.B. St. And.
W. WALKER M.A., M.B. St. And., M.R.C.P. DEPARTMENT OF PHARMACOLOGY AND THERAPEUTICS, QUEEN’S COLLEGE, UNIVERSITY OF ST. ANDREWS, AND CLINICAL INVESTIGATION UNIT, MARYFIELD HOSPITAL, DUNDEE
UNTIL a better understanding of the pathogenesis of thrombotic disease permits a more fundamental and physiological approach to its treatment, it seems likely that long-term therapy with coumarin or indanedione derivatives will have to be given to ever-increasing numbers of patients who have had myocardial infarction or recurrent venous or arterial thrombosis in other parts of the body. The question now at issue is not so much the advisability of this treatment in appropriate cases as the actual selection of the most suitable patients and of the best methods for control of therapy. The problem of organisation is a big one and will doubtless be solved in different ways in different countries and regions. Important suggestions have been made recently by Owren (1959a) in Norway, Wright (1959) in the United States, Toohey (1959) in England, and Douglas (1959) in Scotland. Another problem, relevant to organisation, concerns the laboratory methods that should be used. Once again, unless a particular technique is plainly proved to be superior to all others, the test chosen is almost certain to vary from place to place and the precise manner of its performance will also vary with circumstance. This paper presents an initial assessment of the new and ingenious technique devised by Owren (1959b). Present Methods of Control
the one-stage the " p & p " and Quick (1935), " prothrombin-time " (prothrombin and proconvertin) method of Owren and Aas (1951). The former, besides being a landmark in the physiology of clotting, is still by far the most commonly used method for adjusting coumarin dosage. It is familiar to clinical pathologists and hospital doctors in general who, despite its theoretical and practical shortcomings, have confidence in the method and find it tolerably safe. The methods in
use
of
at
present
are
injected " ketone " was distributed throughout the total body water within a few minutes of injection. The highest concentrations obtained were almost identical in
RESISTANCE TO KETOSIS IN OBESE SUBJECTS A. KEKWICK M.A., M.B. Cantab., F.R.C.P.
all 12 subjects. The
rate
of decline of the blood-levels in
PROFESSOR OF MEDICINE
G. L. S. PAWAN B.Sc. Lond. RESEARCH BIOCHEMIST
T. M. CHALMERS M.D. Edin., M.R.C.P. FIRST ASSISTANT
THE DEPARTMENT OF
MIDDLESEX HOSPITAL MEDICAL
MEDICINE,
SCHOOL, LONDON, W.1
IT has long been recognised that fat people do not readily develop ketosis (Duncan 1959, Kekwick and Pawan 1957). This study was undertaken to try to elucidate the mechanism underlying their resistance. The level of ketone bodies in the blood (acetone, acetoacetic acid, and p-hydroxybutyric acid) depends on the balance between their rate of production by the liver and their rate of utilisation and excretion. Two possible explanations therefore presented themselves: (1) that
the obese could utilise or excrete ketone bodies faster than the non-obese, and thus prevent them accumulating
Fig. 2-Blood " ketonesafter intravenous injection of 60 sodium 0-hydroxybutyrate per kg. body-weight.
mg.
the two groups was similar, suggesting that they utilised the sodium B-hydroxybutyrate at about the same rate. Fig. 2 shows the blood values obtained when twice the above dose was given to 2 obese and 2 non-obese subjects. No difference between the two groups could be seen even when higher initial blood-ketone levels were obtained. Table I shows the amount of ketone bodies recovered in the urine from 5 of the obese subjects and 7 of the nonobese. The striking feature of these figures is the small amount recovered (less than 1% of the dose given). Stadie (1958) and Campbell and Best (1956) have pointed out that isolated organs and intact animals can utilise ketone bodies readily and that probably almost all tissues of the body have this property. The small proportion of the dose recovered here suggests that this is equally true of human subjects, whether obese or non-obese. The two groups,
however, excreted comparable
after intravenous injection of 30 Fig. I-Blood " ketones sodium B-hydroxybutyrate per kg. body-weight. "
mg.
in the body; (2) that the obese did not form ketone bodies so rapidly. To test the first hypothesis sodium B-hydroxybutyrate was given to 6 obese and 6 non-obese subjects. In each the dose was calculated in proportion to body-weight and was administered intravenously (30 mg. of sodium B-hydroxybutyrate per kg. body-weight). As in previous papers (Kekwick and Pawan 1956), the obese were defined as those who had such an obvious excess of subcutaneous fat that no doubt could be entertained in any observer’s mind that they were too fat. The non-obese were selected by a similar criterion: they were manifestly thin. Fig. 1 shows the blood values obtained after injection. The values for " total ketones " are expressed as milligrammes of acetone per 100 ml. of blood and were measured by the method previously published (Pawan 1958).* Recalculating the concentrations obtained in terms of sodium The estimation
it
preceded by oxidation of with acid dichromate.
was
to acetoacetate
B-hydroxybutyrate,
seems
that the
(3-hydroxybutyrate
amounts in the urine. Hence the first hypothesis-that the resistance to ketosis in the obese results from their greater ability to excrete ketone bodies or to utilise them metabolicallydoes not appear to be tenable. An attempt to induce ketosis was next made in 14 obese and 8 non-obese subjects by giving them a diet providing 1000 calories, of which 90% was supplied in the form of fat (Kekwick and Pawan 1956). The criterion of nonobesity in this group was not so rigidly applied as in the first experiment, for we were anxious to discover whether TABLE I-URINARY KETONES EXCRETED DURING VENOUS
INJECTION
OF SODIUM
5
HOURS AFTER INTRA-
B-HYDROXYBUTYRATE
1158 fall in the fasting blood-sugar concentration-a fall which is much less evident in the obese. It can be further noted that this fall took place mainly on the first and second days after starting the diet. Fig. 3 shows that in most subjects the rise in blood ketones took place on or after the second day of the dietary period and was on the whole consequent upon the appearance of hypoglycasmia. The daily carbohydrate intake of the two groups was identical, and amounted to only 12 g. This is clearly less than the daily requirements for both. An obvious possible source of additional carbohydrate Fig. 3-Rise in blood "ketones " in subjects on a 1000-calorie 90%-fat diet. was from body protein, and nitrogen balances were therefore carried out in both those who might wish to reduce weight for cosmetic groups during the dietary period. From fig. 5 it is clear that the non-obese were in negative nitrogen balance reasons were liable to ketosis on a high-fat diet. None of the lean subjects, however, would have been treated as whereas the obese were almost in nitrogen equilibrium. obese patients for medical reasons. TABLE II-FASTING BLOOD-SUGAR LEVELS IN SUBJECTS ON A The relative resistance to ketosis in the obese was con1000-CALORIE 90 "o-FAT DIET firmed. All the obese subjects were able to take the diet for as long as required, whereas 7 of the 8 non-obese subjects had to abandon the diet by the fifth day, and the remaining subject on the eighth day, because of symptoms attributed to ketosis (headaches, anorexia, nausea, &c.). The development of symptoms in different individuals, however, did not appear to be closely related to the height of the blood-ketone levels. Fig. 3 shows the rate of rise in blood ketones in the two groups, and it can be seen that the obese had a slower rise in blood ketones than the non-obese. Fig. 4 shows the output of urinary ketones in the two groups. As might be expected, the amount excreted was much greater in the non-obese. In studies of post-exercise ketosis, Johnson and Passmore (1959) have pointed out that the rate of excretion of acetoacetate is related in a linear manner to the blood concentration, while the excretion of -hydroxybutyrate is exponentially related to blood concentration. Taken in conjunction with the first experiments, these results suggest that resistance to ketosis in the obese results from a diminished production of ketone bodies. It is usually thought that ketone bodies are formed only in the liver (Campbell and Best 1956, Stadie 1958) and of The non-obesehad an average nitrogen balance of -86g. that their rate of formation depends on the values were recorded in both a day as opposed to —l-5g.in the obese; representing a carbohydrates. Blood-sugar the that in Table II shows dietary period. groups during daily breakdown of about 54 g. and 10 g. of protein of the non-obese all but 2 subjects there was a significant respectively. Thus the extra carbohydrate available to the obese could not have come from nitro-
availability
" ketones " (ketone bodies estimated 1000-calorie 90""-fat diet.
Fig. 4-Output of subjects
on a
as
acetone) in the urine in
genous sources. A simple calculation can now be made in respect of the carbohydrate available in the two groups. It is clear (table ill, lines 1, 2, and 3) that in both of them the carbohydrate from the diet or body proteins is far below the minimal daily requirements. It is generally accepted that the human brain utilises carbohydrate as its principal source of energy (Lambertsen et,al. 1953). Blood leaving the brain has a respiratory quotient of 0-97 and the rate of utilisation of oxygen is 5-25 ml. per minute. The needs of the brain alone are therefore of the order of 75 g. glucose a day. Such a figure
1159 4. In non-obese people given a high-fat diet the developketonsemia and ketosis was preceded by a fall in the fasting blood-sugar concentration. In obese people on this diet, there was no such fall or it was small; and they did not develop ketosis to any significant degree. 5. Reasons are given for believing that net conversion of fat to carbohydrate took place in both groups. It is suggested that obese people may be able to turn fat into carbohydrate at a higher rate than non-obese people.
ment of
Fig. 5-Nitrogen balances in subjects for 4-14 days.
on a
1000-calorie 90%-fat diet
is almost certainly on the low side. Doubtless other organs also require some carbohydrate for their normal metabolism. Table in, lines 4 and 5, extends this calculation to show that neither group of subjects was getting enough carbohydrate to supply even the brain alone with its daily needs, and that the apparent deficit in the obese group was much the greater. Both groups therefore must have obtained carbohydrate from some other source, and it is our belief they could obtain it only from fat.Such a conclusion is by no means new (Lyon et al. 1932). The evidence both for and against the possibility is summed up by Weinman et al. (1957). They conclude that it is still uncertain whether conversion of fat to carbohydrate with a net gain in carbohydrate can take place in man; but it is difficult to escape the conclusion that it must have happened in these
We should like to thank Miss E. Wilkinson Hughes, principal dietitian, Middlesex Hospital; Miss M. Clode for biochemical help; Miss C. M. Evans for secretarial assistance; and two ward sisters, Miss R. S. Starkey and Miss J. Ward. REFERENCES
-
subjects. clear that in man the minimal daily needs for carbohydrate lie between 75 g. a day (the amount necessary for brain metabolism) and 400 g. a day (the normal carbohydrate intake). There is, however, no evidence that the daily needs are the same for the two groups studied here. The minimal needs may well be less in the obese because It
seems
TABLE
III-SUMMARY OF DAILY CARBOHYDRATE BALANCES NON-OBESE AND OBESE GROUPS ON 90%-FAT DIET
IN
THE
other sources of energy, such as fatty acids, can be more readily used by the tissues. If this is not so, the data suggest that obese people can produce more carbohydrate from non-protein sources (i.e., from fat).
Summary 1. It is much more difficult to induce ketosis in obese than in non-obese people. 2. The difference does not appear to depend on a higher rate of utilisation or excretion of ketone bodies by the obese. After intravenous injection of sodium &bgr;-hydroxybutyrate the rate of disappearance of this ketone body from the blood was found to be the same in obese as in non-obese people. Less than 1 % of the injected dose was excreted in the urine: the amount excreted was the same in the two groups. 3. Presumably, then, the rate of production of ketone bodies is less in the obese.
t
S. B. Furnass
(unpublished data) has found twenty-four-hour protein respiratory quotients around 0-7 in obese subjects 1000-calorie 90%-fat diet.
nonon a
Campbell, J., Best, C. H. (1956) Metabolism, 5, 95. Duncan, G. G. (1959) Diseases of Metabolism. Philadelphia. Johnson, R. E., Passmore, R. (1959) J. Physiol. 146, 51P. Kekwick, A., Pawan, G. L. S. (1956) Lancet, ii, 155. (1957) Metabolism, 6, 447. Lambertsen, C. J., Kough, R. H., Cooper, D. Y., Emmel, G. L., Loeschcke, H. H., Schmidt, C. F. (1953) J. appl. Physiol. 5, 471. Lyon, D. M., Dunlop, D. M., Stewart, C. P. (1932) Biochem. J. 26, 1107. Pawan, G. L. S. (1958) ibid. 68, 33P. Stadie, W. C. (1958) Diabetes, 7, 173. Weinman, E. O., Strisower, E. H., Chaikoff, I. L. (1957) Physiol. Rev. 37, 252. —
—
CONTROL OF ANTICOAGULANT THERAPY A TRIAL OF THROMBOTEST
J. M. MATTHEWS M.B. St. And.
W. WALKER M.A., M.B. St. And., M.R.C.P. DEPARTMENT OF PHARMACOLOGY AND THERAPEUTICS, QUEEN’S COLLEGE, UNIVERSITY OF ST. ANDREWS, AND CLINICAL INVESTIGATION UNIT, MARYFIELD HOSPITAL, DUNDEE
UNTIL a better understanding of the pathogenesis of thrombotic disease permits a more fundamental and physiological approach to its treatment, it seems likely that long-term therapy with coumarin or indanedione derivatives will have to be given to ever-increasing numbers of patients who have had myocardial infarction or recurrent venous or arterial thrombosis in other parts of the body. The question now at issue is not so much the advisability of this treatment in appropriate cases as the actual selection of the most suitable patients and of the best methods for control of therapy. The problem of organisation is a big one and will doubtless be solved in different ways in different countries and regions. Important suggestions have been made recently by Owren (1959a) in Norway, Wright (1959) in the United States, Toohey (1959) in England, and Douglas (1959) in Scotland. Another problem, relevant to organisation, concerns the laboratory methods that should be used. Once again, unless a particular technique is plainly proved to be superior to all others, the test chosen is almost certain to vary from place to place and the precise manner of its performance will also vary with circumstance. This paper presents an initial assessment of the new and ingenious technique devised by Owren (1959b). Present Methods of Control
the one-stage the " p & p " and Quick (1935), " prothrombin-time " (prothrombin and proconvertin) method of Owren and Aas (1951). The former, besides being a landmark in the physiology of clotting, is still by far the most commonly used method for adjusting coumarin dosage. It is familiar to clinical pathologists and hospital doctors in general who, despite its theoretical and practical shortcomings, have confidence in the method and find it tolerably safe. The methods in
use
of
at
present
are