156 



COMPARATIVE PHYSIOLOGY. 



of the blood about &,000,000 for the male and 500,000 less for 

 the female, which would furnish about 250,000,000,000 in a 

 pound of blood. It will be understood that averages only are 

 spoken of, as all kinds of variations occur, some of which will 

 be referred to later, and their significance explained. The size 

 of the corpuscles in the domestic animals is variable — a matter 

 of importance when transfusion of blood is under consideration. 

 Under the microscope the blood of vertebrates is seen to owe 

 its color to the cells chiefly, and, so far as the red goes, almost 



wholly. Corpuscles 

 when seen singly are 

 never of the deep red, 

 however, of the blood 

 as a whole, but rather 

 a yellowish red, the 

 tinge varying some- 

 what with the class of 

 animals from which 

 the specimen has been 

 taken. 



Certain other mor- 

 phological elements 

 found in mammalian 

 blood deserve brief 

 mention, though their 

 significance is as yet 

 a matter of much dis- 

 pute. 



1. The blood-plates 

 (plaques, hcematoblasts, third element), very small, colorless, 

 biconcave disks, which are deposited in great numbers on any 

 thread or similar foreign body introduced into the circulation, 

 and rapidly break up when blood is shed. 



2. On a slide of blood that has been prepared for some little 

 time, aggregations of very minute granules (elementary gran- 

 ules) may be seen. These are supposed to represent the disin- 

 tegrating protoplasm of the corpuscles. 



The pale or colorless corpuscles are very few in number in 

 mammals compared with the red, there being on the average 

 only about 1 in 400 to 600, though they become much more 

 numerous after a meal. They are granular in appearance, and 

 possess one or more nuclei, which are not, however, readily 



Pig. 141.— Corpuscles from human subject (Funke). 

 A few colorless corpuscles are seen among the col- 

 ored disks, which are many of them arranged in 

 rmUeaux. 



