2H A Manual of Veterinary Physiology. 



animals ; its greatest interest lies perhaps in the parr it was 

 supposed to play in the process of coagulation — a part 

 which we have now good reason to believe does not exist. 

 Fibrinogen is the precursor of fibrin in the blood — a sub- 

 stance we shall have more to say about in dealing with 

 coagulation — it is found in blood plasma, but not in the 

 serum; it also exists in the fluids thrown out in t < > the 

 cavity of the chest, pericardium, etc. 



Corpuscles of the Blood. — Ittood examined under the 

 microscope is found to consist of an enormous number of 

 bodies termed corpuscles floating in the liquor sanguinis. 

 These corpuscles are found to be both red and white ; the 

 former are by far the more numerous, the latter are the 

 larger. 



The Red Corpuscles, viewed under the microscope, are bi- 

 concave discs, circular in shape, and possessing no nucleus, 

 though, owing to their shape certain focussing may produce 

 a dark centre Avhich might be mistaken for a nucleus, but 

 which is really due to the shape of the body, and is, there- 

 fore, an optical effect. The red cells have a tendency to lie 

 on top of each other in the form of piles of pence, this con- 

 dition is spoken of as forming rouleaux, and its cause is 

 unknown. The circular shape of the red cell is affected by 

 the amount <>f fluid in the blood : where the latter is small. 

 as occurs in many diseases, the corpuscles become covered 

 with spines or projections ; when the fluid is in excess the 

 corpuscles swell. The opacity of blood is due to the con- 

 cave character of the corpuscles, reflecting light as from 

 concave mirrors (M'Kendrick). When the corpuscles are 

 destroyed the blood becomes transparent. 



A red blood coll is composed of a stroma, holding in its 

 meshes the red colouring matter. The stroma or frame- 

 work of the corpuscle consists of an albuminous material 

 allied to the globulins, ami a fatty matter termed lecithin. 

 The red colouring matter consists of an albuminous crystal- 

 line substance hremoglobin. The whole of these are con 

 tained in the corpuscle, not by means of an envelope, but. 

 retained in the pores of the stroma. 



