112 THE BLOOD. 



different animals. This point is interesting from the fact 

 that it is often an important question to determine whether a 

 given specimen of blood be from the human subject or one 

 of the inferior animals. Comparative measurements also 

 have an interest on account of a relation which seems to 

 exist in the animal scale between the size of the blood-cor- 

 puscles, and muscular activity. In all the mammalia, with 

 the exception of the camel and lama, in which they are oval, 

 the blood-corpuscles have the same anatomical characters as 

 in the human subject ; the only difference is in size. In only 

 two animals, the elephant and sloth, are they larger than in 

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

 diameter. By reference to the table it will be seen that in 

 some animals the corpuscles are very .much smaller than in 

 man ; and by accurate measurement, we are enabled to dis- 

 tinguish their blood from the blood of the human subject. 

 But in forming an opinion on this subject, it must be remem- 

 bered that there is some variation in the size of the corpuscles 

 of the same animal. We can easily distinguish the blood of 

 the human subject, or of the mammals generally, from that 

 of birds, fishes, or reptiles ; for in these classes of animals the 

 corpuscles are oval and contain a granular nucleus. 



Milne-Edwards has attempted to show, by a comparison 

 of the diameter of the blood-corpuscles in different species, 

 that their dimensions are in inverse ratio to the muscular 

 activity of the animal. 1 Reference to the table will show 

 that this relation holds good to a certain extent, while there 

 certainly exists none between the size of the corpuscle and 

 the size of the animal. In deer, which are remarkable for 

 their muscular activity, the corpuscles are very small, j^V^ 

 of an inch ; while in the sloth they are j-s o"? an d i n the ape, 

 which is comparatively inactive, ^Vo- But, on the other 

 hand, in the dog, which is quite active, we have a corpuscle 



1 MILNE-EDWARDS, Lemons sur la Physiologic et V Anatomic Comparee, 

 tome i., p. 57 et seq. 



