NUMBER OF BLOOD-CELLS. 121 



Constituted thus of an elastic sac filled with globulin and hsematin, the 

 cells float in the plasma. They are nourished at its expense, and when 

 they die, deliver up their contents Iby deliquescence to it. Accompany- 

 ing them are the white corpuscles, from which new generations are to 

 arise. It is usually stated that for every 50 red discs there The white 

 is one white corpuscle. They may be readily discovered dur- cor P uscle s- 

 ing the circulation by the microscope, many of them occupying the exte- 

 rior of the current, as though they had a special relation to the soft tis- 

 sues. It may perhaps be erroneous to regard these large white corpus- 

 cles as the embryos of the red discs. Reasons could be assigned in sup- 

 port of the doctrine that the same primitive germ going onward to devel- 

 opment may, at a certain point, diverge in two directions ; if it passes 

 through one, it will perfect itself as a white cell; if through the other, as a 

 red disc. 



The proportional number of blood corpuscles in different animals va- 

 ries considerably. Generally cold-blooded mammals present Number of cells 

 fewer than warm-blooded ones, birds having more than quad- 

 rupeds, and among these the carnivora more than the herbiv- 

 ora. Of different domestic animals, the pig, the dog, the ox, the horse, 

 the cat, the sheep, the goat, possess them in the order in which their 

 names have been mentioned, the goat having only 86 to 145 in the pig. 

 Their proportional number also varies in different regions of the circula- 

 tion ; thus it is said that arterial blood contains fewer than venous, the 

 portal blood fewer than the jugular, the hepatic more than the portal. It 

 is not, however, to be overlooked, that in all these determinations the 

 quantity of water which chances to be present controls the estimates, and 

 that therefore, as thus offered, they are really of less interest than might 

 at first sight be supposed. 



We have next to speak of the plasma. It may be described as a clear 

 and slightly yellowish colored fluid, consisting, as all animal composition 

 juices do, for the most part of water, holding in suspension or of plasma, 

 solution albumen, fibrin, fats, and various mineral bodies, as the follow- 

 ing analysis shows. 



Proximate Composition of the Plasma. 



Water 902.90 



Albumen 78.84 



Fibrin 4.05 



Fat 1.72 



Extractive 3.94 



Mineral substances 8.55 



1000.00 



Of the water it may be remarked, that the usual percent- Water of the 

 age estimate made of its quantity, as regards the entire blood, whole blood : 

 is from 700 to 790 parts in 1000. Within these limits it is its variations - 



