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DISTINCTIONS BETWEEN CAPILLARY AND OTHER BLOOD-VESSELS.
540 vital power of muscles, appear to take place vessels is somewhat more complex; the especially in others, and therefore affect capillaries are more abundant; the arteries,
in number to the direct course ; and the veins are larger and more tortuous. No pulsatory movement can be perceived in the blood while moving in the capillaries or veins, as long as the circulation is unim. peded and in the natural state. The author was unable to detect any anastomoses between the minutc arteries, although they are frequent among the veins, where they give rise to occasional oscillations in the currents of blood flowing through them : neither could lie discover any instance, in the web of the frog, of the immediate termination of an artery in a vein. The velocity of the blood is retarded immediately in its passage from the arteries into the capillaries, because the united capacity of the branches is greater DISTINCTIONS BETWEEN than that of the trunk which divides to form CAPILLARY AND OTHER BLOOD- them. In the mesentery of the toad the disVESSELS. tribution of the vessels is simple, like thatof the fins and tail of a fish. But in the pulmoTHE following outline of a paper ’‘ On nary organs, where the purpose to be answerthe Anatomy and Physiology of the Minute ed is that of diffusing the blood over the and Capillary Vessels," by Dr. Marshall greatest possible extent of surface, the arte. Hall, which was read a short time since at ries and the veins correspond to each other the Royal Society, contains some observa- in all their ramifications, and their adjacent tions of considerable interest :-The author branches generally pursue courses parallel considers the minute blood-vessels as ar- to each other. Their transition into capilteries or veins, as long as their subdivisions laries is effected with fewer subdivisions or junctions are attended with a change in than in the case of other arteries. No distheir dimensions. When no such change position exists among these arteries to form occurs, he denominates them capillaries. anastomoses with each other, or with the With the aid of an achromatic microscope of veins ; but the intervening spaces are uni. Dolland, he endeavoured to ascertain what formly occupied by a close network of ca. differences existed between the systemic pillary vessels. The lung of the salamander and pulmonary circulations, as far as regards is simply vesicular; that of the frog is cel. these vessels. Dr. Edwards had observed, lular as well as vesicular, and that the batrachian reptiles are speedily presents greater difficulty in following with killed by immersion in hot water ; and Dr. the microscope the coujse of the vessels Halt found, that although by plunging ani- as they traverse membranes situated in mals of that order into water at 1200 of different planes. In the lungs of the frog, Fahrenheit they were speedily deprived of the larger vessels pass chiefly on the exterall power of sensation and of motion, yet that nal surface ; but in the toad they follow the the action of the heart continued for a very course of the internal margins of the verti. long time, thus affording an opportunity of cal meshes. The author concludes from his leisurely observing the phenomena of the observations, that the capillaries, properly circulation, without the infliction of pain, so called, have no power to contribute to and without any disturbance from the strug- the motion of the blood, and that the capilgles of the animal. lary circulation depends altogether upon the -In the fins and tail of the stickleback, the action of the heart and arteries. In cases number of the capillary vessels is small, and of impeded circulation, he observes, the their distribution simple ; the artery runs pulsatory movement of the blood may be along the border of each ray till it reaches seen, not only in the arteries, but also in the extremity, when it is reflected, and be- the capillary vessels, and even in the veins. coming a vein, pursues a retrograde course by the side of the artery. This simplicity CONTENTS OF THE VENA PORTÆ. in the mode of its distribution corresponds with the simple nature of the function of the A PAPER was lately read at the Royd part, which is merely an instrument for Society, entitled "An Examination of the swimming. In theweb of the frog’s foot, Blood found in the Vena Portæ; by Dr. which is adapted to a greater variety of James Thackeray." The author, in the mechanical purposes, the system of bloodof an inquiry into the properties of
other muscles ; and the same g. a violent concussion) which produces one of these effects exclusively in i one nerve, may produce the other in another nerve immediately adjoining it. Is These facts seem sufficient to show, that if it be galvanism which enables nerves to act on muscles in the living body, it is galvanism excited by means, and subjected to laws, veidifferent from what we observe in examining the galvanic phenomena of dead matter. And this is equivalent to saying that nerves act on muscles in the hving body, in virtue of certain vital powers:’
especially cause
(e.
which
are
nearly equal
veins, pursue
a more
consequently
course
in number to the direct course ; and the veins are larger and more tortuous. No pulsatory movement can be perceived in the blood while moving in the capillaries or veins, as long as the circulation is unim. peded and in the natural state. The author was unable to detect any anastomoses between the minutc arteries, although they are frequent among the veins, where they give rise to occasional oscillations in the currents of blood flowing through them : neither could lie discover any instance, in the web of the frog, of the immediate termination of an artery in a vein. The velocity of the blood is retarded immediately in its passage from the arteries into the capillaries, because the united capacity of the branches is greater DISTINCTIONS BETWEEN than that of the trunk which divides to form CAPILLARY AND OTHER BLOOD- them. In the mesentery of the toad the disVESSELS. tribution of the vessels is simple, like thatof the fins and tail of a fish. But in the pulmoTHE following outline of a paper ’‘ On nary organs, where the purpose to be answerthe Anatomy and Physiology of the Minute ed is that of diffusing the blood over the and Capillary Vessels," by Dr. Marshall greatest possible extent of surface, the arte. Hall, which was read a short time since at ries and the veins correspond to each other the Royal Society, contains some observa- in all their ramifications, and their adjacent tions of considerable interest :-The author branches generally pursue courses parallel considers the minute blood-vessels as ar- to each other. Their transition into capilteries or veins, as long as their subdivisions laries is effected with fewer subdivisions or junctions are attended with a change in than in the case of other arteries. No distheir dimensions. When no such change position exists among these arteries to form occurs, he denominates them capillaries. anastomoses with each other, or with the With the aid of an achromatic microscope of veins ; but the intervening spaces are uni. Dolland, he endeavoured to ascertain what formly occupied by a close network of ca. differences existed between the systemic pillary vessels. The lung of the salamander and pulmonary circulations, as far as regards is simply vesicular; that of the frog is cel. these vessels. Dr. Edwards had observed, lular as well as vesicular, and that the batrachian reptiles are speedily presents greater difficulty in following with killed by immersion in hot water ; and Dr. the microscope the coujse of the vessels Halt found, that although by plunging ani- as they traverse membranes situated in mals of that order into water at 1200 of different planes. In the lungs of the frog, Fahrenheit they were speedily deprived of the larger vessels pass chiefly on the exterall power of sensation and of motion, yet that nal surface ; but in the toad they follow the the action of the heart continued for a very course of the internal margins of the verti. long time, thus affording an opportunity of cal meshes. The author concludes from his leisurely observing the phenomena of the observations, that the capillaries, properly circulation, without the infliction of pain, so called, have no power to contribute to and without any disturbance from the strug- the motion of the blood, and that the capilgles of the animal. lary circulation depends altogether upon the -In the fins and tail of the stickleback, the action of the heart and arteries. In cases number of the capillary vessels is small, and of impeded circulation, he observes, the their distribution simple ; the artery runs pulsatory movement of the blood may be along the border of each ray till it reaches seen, not only in the arteries, but also in the extremity, when it is reflected, and be- the capillary vessels, and even in the veins. coming a vein, pursues a retrograde course by the side of the artery. This simplicity CONTENTS OF THE VENA PORTÆ. in the mode of its distribution corresponds with the simple nature of the function of the A PAPER was lately read at the Royd part, which is merely an instrument for Society, entitled "An Examination of the swimming. In theweb of the frog’s foot, Blood found in the Vena Portæ; by Dr. which is adapted to a greater variety of James Thackeray." The author, in the mechanical purposes, the system of bloodof an inquiry into the properties of
other muscles ; and the same g. a violent concussion) which produces one of these effects exclusively in i one nerve, may produce the other in another nerve immediately adjoining it. Is These facts seem sufficient to show, that if it be galvanism which enables nerves to act on muscles in the living body, it is galvanism excited by means, and subjected to laws, veidifferent from what we observe in examining the galvanic phenomena of dead matter. And this is equivalent to saying that nerves act on muscles in the hving body, in virtue of certain vital powers:’
especially cause
(e.
which
are
nearly equal
veins, pursue
a more
consequently
course