8 



THE BLOOD. 



exception of the camel and llama, in which the corpuscles are oval, the 

 blood has nearly the same anatomical characters as in the human subject. 

 In only two animals, the elephant and sloth, are the red corpuscles larger 

 than in man; and in all others, they are smaller or of nearly the same 

 diameter. In some animals, the corpuscles are very much smaller than in 

 man, and by accurate measurements, their blood can be distinguished from 

 the blood of the human subject ; but in forming an opinion on this subject, 



it must be remembered that there is 

 some variation in the size of the cor- 

 puscles of the same animal. The 

 blood of the human subject or of the 

 mammals generally can be readily dis- 

 tinguished from the blood of birds, 

 fishes or reptiles; for in these ani- 

 mals, the corpuscles are oval and con- 

 tain a granular nucleus. 



Milne-Edwards has attempted to 

 show, by a comparison of the diameter 

 of the blood - corpuscles in different 

 species, that their size bears an inverse 

 ratio to the muscular activity of the 

 _ animal. This relation holds good to 



FIG. 3. Blood-corpuscles of the frog ; magnified , , 



370 diameters (from a photograph taken at some extent, while there certamlv ex- 



the United States Army Medical Museum). 



ists none between the size of the cor- 

 puscles and the size of the animal. In deer, animals remarkable for 

 muscular activity, the corpuscles are very small, g * 00 of an inch (5 ft) ; 

 while in the sloth they are -g-gVir (8*9 /*)> an( l i n the ape, which is com- 

 paratively inactive -j^^o (7*7 /*) On the other hand, in the dog, which is 

 quite active, the corpuscles measure -J-^QT f an i ncn CM? /*)> an( i i n the ox > 

 which is certainly not so active, the diameter of the corpuscles is T fVir of an 

 inch (6/1). Although this relation between the size of the blood-corpuscles 

 and muscular activity is not invariable, it is certain that, the higher the 

 animal in the scale, the smaller are the blood-corpuscles ; the largest being 

 found in the lowest orders of reptiles, and the smallest, in the mammalia. 

 The blood of the invertebrates, with a few exceptions, contains no colored 

 corpuscles. 



Enumeration of the Blood-Corpuscles. In most of the quantitative analy- 

 ses of the blood, the proportion of moist corpuscles to the entire mass of blood 

 is stated to be a little less than one-half. This estimate is necessarily rather 

 rough; and it would be useful to ascertain, if possible, the normal varia- 

 tions in the proportion of corpuscles, under different conditions of the sys- 

 tem, particularly as these bodies play so important a part in many of the 

 functions of the organism. Actual enumerations of the blood-corpuscles 

 have been made by Vierordt, Weckler, Malassez and others. It is stated by 

 Malassez that the error in his calculations is not more than two or three per 

 cent. The process employed by Malassez is the following : 



