Page:The American Cyclopædia (1879) Volume II.djvu/748

 728 BLOOD full account of the historical and legendary data respecting Blondel and an edition of his and Richard's songs. BLOOD, in man and the higher animals, the red liquid which circulates in the cavities of the heart, the arteries, the veins, and the capil- lary vessels. I. PHYSICAL QUALITIES OF THE BLOOD. In the living hody the blood is a some- what tenacious liquid, containing innumerable solid particles (the blood globules), which are seen only with the microscope. In the arteries the blood is more or less of a light vermilion tint in children, and of a purplish or bright cherry red in adults, and somewhat darker in old people and in pregnant women. In the veins it is dark red, and even blackish. In disease, and also in various physiological states, the blood may be very dark in the arteries, and in other cases very bright in the veins. The peculiar odor of the blood usually resem- bles that of the perspiration of the individual from whom the blood has heen taken. The blood is transparent when seen in thin layers ; opaque otherwise. The specific gravity of nor- mal human blood averages 1-055, its physio- logical limits being 1-045 and 1 '075. The min- imum of density is in pregnant women and in children, and the maximum in adult men. The capacity of the blood for heat is, according to Nasse, in an exact ratio to its density. II. QUANTITY OP BLOOD IN THE HUMAN BODY. Of the various means employed to find out the relative amount of blood in the body, that which consists in first weighing an animal, then taking out as much of its blood as possible, and weighing the latter, is not to be relied on, as the blood never flows out entirely from the blood vessels. However, as it is interesting to know how much blood may escape from divided blood vessels, we will give a list of the results obtained by various experiments. In the ewe the weight of the blood is to the weight of the body as 1 to 22 or 23; in the ox as 1 to 12 (Herbst), or 1 to 23 or 24 (Wanner) ; in the cow, as 1 to 21 -77 ; in the sheep, as 1 to 20 or 27-72 ; in the dog, as 1 to 10 or 12, or 21 ; in the horse, as 1 to 18; in the lamb, as 1 to 20 or 22 ; in the cat, as 1 to 22 ; in the rabbit, as 1 to 24 or 29 ; in the ass, as 1 to 23 ; in the fox, as 1 to 21 ; in the mouse, as 1 to 22'5. From these results, it has been concluded that in man the proportion of blood is from ^ to T V, and therefore, for a man weighing 160 Ibs., the quantity of blood is from 8 to 16 Ibs. But Haller relates many cases of hemorrhage in which men and women have lost 9, 10, 11, 15, 18, or 22 Ibs., or even 30 Ibs. of blood from the nose, and 12 Ibs. in one night, or 8 pints, by vomiting (gastrorhagid). Burdach says that Wrisberg has seen a woman who died from a loss of 26 Ibs. of blood from the uterus, and that another woman after decapitation yielded 24 Ibs. of blood. From facts of this kind Hal- ler, Quesnay, and Hoffmann inferred that there is about 28 Ibs. of blood in the body of a man of average size. The best mode of estimating the amount of blood in a man has been cm- ployed by Lehmann and E. Weber. They determined the weight of two criminals both before and after decapitation. The quantity of the blood which escaped from the body was ascertained in the following manner : water was injected into the vessels of the trunk and head, until the fiuid escaping from the veins had only a pale red or yellow color ; the quan- tity of the blood remaining in the body was then calculated, by instituting a comparison between the solid residue of this pale red aque- I ous fluid, and that of the blood which first I escaped. By way of illustration, we subjoin I the results yielded by one of the experiments. The living body of one of the criminals weighed 60,140 grammes, and the same body, after de- capitation, 54, 600 grammes; consequently, 5,540 grammes of blood had escaped ; 28-56 grammes of this blood yielded 5-36 grammes of solid residue; 60-5 grammes sanguineous water, col- lected after the injection, contained 3-724 grammes of solid substances; 6-050 grammes of the sanguineous water that returned from the veins were collected, and these contained 37'24 grammes of solid residue, which corresponds to 1,980 grammes of blood ; consequently, the body contained 7,520 grammes of blood (5,540 escaping in the act of decapitation, and 1,980 remaining in the body) ; hence, the weight of the whole of the blood was to that of the body nearly in the ratio of 1 to 8. The other ex- periment yielded a precisely similar result. By this mode of calculation, which gives a nearer approximation than any other to the propor- tion of blood, we have not, however, the exact proportion, because blood remains in some of the capillaries. The only positive conclusion we can draw from these experiments is that there is at least 20 Ibs. of blood in the body of a healthy man weighing 160 Ibs. Valentin has employed another mode of calculation, which, unlike the preceding, has given a pro- portion of blood in the body greater than that which really exists. He bleeds an animal, and determines the proportion of solid parts in the blood ; then a certain quantity of water is injected into the veins, and immediately after- ward blood is drawn again, and its proportion of solid parts determined ; and after a compar- ison of the two results, a calculation is made which gives the quantity of blood. In dogs it was found that the amount of blood, com- pared to the weight of the body, is as 1 to 4, and in sheep as 1 to 5. If this result be ap- plied to man, we find, for a man weighing 160 Ibs., from 32 to 36 Ibs. of blood, which is most probably an over-estimate. Dr. Blake, by an- other method, has obtained more important results. He injects into the veins of an animal a certain quantity of the sulphate of alumina, a salt which is not quickly destroyed in the blood, or expelled from it; then he analyzes the blood, and by the proportion of this salt found in it he ascertains very nearly the quan- tity of blood in the body of the animal. The