732 BLOOD blood fibrinous flakes. Ilenle at first consider- ed these particles as shreds of epithelium, from the lining membrane of the blood vessels ; after- ward as aggregations of cell membranes of de- stroyed blood disks. Lehmann admits that ex- periments of Doderlein have proved that these flakes are not composed of coagulated fibrine. Bruch has tried to show that the pretended fibrinous flakes are nothing more than epithe- lial cells from the skin of the observer himself, which have fallen from his face or his hands on the preparation. It is very probable that these flakes are in a great measure, but not entirely, composed of epithelial cells, and that truly coagulated fibrine, in more or less small particles, exists in blood out of the blood vessels, at least. Besides the morpho- logical elements above described, we find in the blood of certain inferior animals vibriones, or other infusoria, and microscopical drops of fat. The assumed presence in the blood of another distinct element, i. e., the lymph or chyle cor- puscle, has received a different interpretation from that previously admitted : the colorless or pale corpuscles of the blood have been proved to be similar to the chyle or lymph corpuscles. V. COAGVLATION OF THE BLOOD. When drawn from a vein or an artery of man, blood usually begins to coagulate in a few minutes. From the liquid state it passes at first to the condition of a soft jelly, which gradually becomes more and more consistent. The whole mass of the blood seems in the beginning to become solid, but by the contraction of the coagulated sub- stance the liquid is expelled from the kind of network formed by this substance, and the coagulum or clot gradually becomes smaller. The part of the blood which remains liquid is called serum. It had been imagined that the coagulation of the blood depended upon the ad- hesion of the blood corpuscles one to the other ; but it is now well known that the coagulation is only the result of the solidification of the fibrine, which, taking place in the whole mass of the blood, contains the blood corpuscles impris- oned in the network it forms. The following table shows what changes take place in the blood during coagulation : Liq. blood Liquor Blood corpuscles. brine i )- C'oag. vClot ( blood. The serum is the liquor sanguinis deprived of its fibrine, and no longer holding the corpuscles ; the clot is the fibrine solidified, and holding the blood corpuscles. It is well proved that the co- agulation of the blood, removed from the body, depends upon the coagulation of its fibrine. If blood drawn from the vessels of a living man or animal be whipped with glass rods, its fibrine becomes solidified on these rods, and the whole of it may in this manner be taken away, and then the defibrinated blood remains liquid. Nevertheless, many blood corpuscles sometimes adhere one with another, and in so doing offer a half solid mass at the bottom of the vase, but the least motion shows that there is no coagu- lation. When they are included in a fibrinous clot, the blood corpuscles contribute to its so- lidification by some slight adhesion with the fibrine, and by their being included in its net- work. The circumstances which influence the coagulation of the blood have been the subject of a great many investigations, among which the most important are those of Hewson, John Davy, T. Thackrah, C. Scudamore, Gulliver, and more recently Zimmermann, E. Brucke. and B. W. Richardson. We will examine here only what relates to the principal circumstances and assumed causes of the coagulation of the blood. 1. Influence of temperature. The co- agulation of the blood drawn from the blood vessels does not depend upon the loss of its tem- perature. It is true that the blood flowing from the vein of a man in a room, even at a summer temperature, soon loses several degrees of heat, and falls from 102 to 98, or to a lower degree.* But this loss of a few degrees of heat cannot be the cause of the coagulation of the blood, because every day, during the win- ter, our blood, in the nose, in the ears, and the extremities of the limbs, loses many more de- grees without coagulating. Besides, the blood of cold-blooded animals coagulates as well as that of the warm-blooded. Ilewson has dem- onstrated that it is possible to freeze the blood while yet fluid, and that after being rendered fluid again by thawing, it will coagulate in the ordinary way. Hunter succeeded in freezing the blood in the ear of a living rabit, and after some time, being thawed, it did not coagulate. A low temperature retards coagulation, but the physiologists who maintain that coagulation is prevented by a temperature near the freezing point are mistaken. Brucke says that he has seen blood coagulated at every temperature above 32 F., and even below that point, provi- ded the blood itself was not frozen. But he has seen the blood of frogs sometimes remain fluid for eight days, while kept in the snow. Brown- Sequard has seen the blood of frogs coagulated so quickly at a temperature of 33 or 34 F., or a little above, that hemorrhage from the section of one third of the ventricular mass of the heart was stopped by a clot, and life was maintained. As a general rule, however, the higher the tem- perature, within certain limits, the sooner co- agulation takes place ; but it seems, according to Gulliver, that the coagulating power is lost by a temperature of 150 F., as blood heated to that point remains permanently fluid. The experiments of Polli, Trousseau, Leblanc, and others, seem to show that the temperature most favorable to coagulation is very nearly that of the blood itself. 2. Influence of air. Many physiologists have thought that the cause of the coagulation of the blood, when drawn
- The temperature of the blood is erroneously marked at
98 on the thermometers. Experiments made by John Davy and by Brown-Squard have shown that, at least in the abdomen and in the chest, the blood in man is at a higher de- gree. According to the last-named experimenter, it is be- tween 10-2 and 1P8.
