A MANUAL OF VETERINARY PHYSIOLOGY 



but if it has undergone coagulation and fibrin (false membranes) 

 has been formed, then the resulting fluid is serum. 



In the following table is shown the composition of the blood 

 plasma of different animals. The figures are expressed as 

 grammes in ioo c.c. of blood. It will be observed that in the 

 horse the globulins exceed the albumins, while in the dog and 

 pig the reverse holds good. The poverty of dog's blood in total pro- 

 teins, as compared with that of the horse and pig, is also striking. 



So long as the blood is in circulation or prevented from clotting, 

 its fluid portion is termed ' plasma ' ; but if blood be allowed to 

 coagulate, in course of time it separates into a solid clot and a 

 liquid portion, and this liquid is no longer known as plasma, but 

 as serum. Serum is therefore plasma which is modified as the 

 result of coagulation, and as this latter process is attended by 

 the production of fibrin, it may be said that serum is plasma 

 minus the fibrin-forming elements. 



Serum does not contain fibrinogen, for the reason that the latter 

 has been used up in the process of clotting, but it possesses, in 

 addition to serum-albumin and paraglobulin, a body known as 

 fibrino-globulin, believed to be split off from fibrinogen in the 

 act of clotting, and nucleo-protein, supposed to be derived from 

 the fibrin ferment ; some observers doubt the existence of this 

 latter substance in the serum. The total protein content of 

 serum is 8 or 9 per cent., and so resembles the protein content of 

 plasma ; the extractives and salts are the same in both fluids. 



In the following table a comparison is made between the 

 proteins of plasma and serum : 



Plasma. 



Serum-albumin, 



Paraglobulin. 



Fibrinogen. 



Serum. 



Serum-albumin . 

 Paraglobulin. 

 Fibrino-globulin . 

 Nucleo-protein. 



Corpuscles. — Blood examined under the microscope is found 

 to consist of an enormous number of bodies termed ' corpuscles,' 

 floating in the liquor sanguinis. These corpuscles are of two 

 kinds, red and white ; the former are the more numerous, the 

 latter are the larger. 



