26 A MANUAL OF VETERINARY PHYSIOLOGY 



Transfusion of warm normal or physiological saline solution 

 (NaCl o-g per cent.) is capable of keeping the heart beating even 

 after severe haemorrhage, showing that the immediate essential 

 factor is the restoration of bulk to the empty vascular system. 

 Transfusion of blood is not without danger, for, as has been 

 shown in dealing with haemolysis, the serum of one animal may 

 be toxic to another. 



The Gases of the Blood are more conveniently dealt with in 

 the chapter on Respiration (see p 121). 



Composition of the Blood. — Reviewing the various analyses 

 which have been published of the blood of animals, the following 

 represents the average composition of the fluid : 



The Plasma. 

 Water ______ go parts per cent. 



Proteins - - - - - -8 or 9 parts. 



Fats - - - - - - -o*i part. 



Extractives - - - - - 0-4 ,, 



Salts - - - - - - - o-8 „ 



The Corpuscles. 



These represent from one- third to half the weight of the blood, 

 and consist of — 



Water - - 64 parts per cent. 



Solids - - 35 „ consisting of 32 per cent, haemo- 

 globin, o*i per cent, proteins. 

 Salts - - 1 part. 



Taking the blood as a whole, the following represents approxi- 

 mately its composition in every 100 parts : 



The Blood in Disease. — The blood plays two distinct parts in 

 disease : it is a carrier and distributer of infection to the body-cells, 

 and, further, it may itself undergo profound pathological change. 



All the specific infective diseases of animals are spread through the 

 body by means of the blood-stream. It is true that the initial source 

 of entry may be an allied passage — the lymph-stream — but it is by 

 means of the blood that the final and complete invasion of the body 

 is effected. Nor does this observation apply to specific diseases only ; 

 if we take two such opposite conditions as anthrax and poisoning by 

 arsenic, it is the blood in each case which is responsible for the dis- 

 tribution of the infecting agent. 



The blood-tissue itself may be the seat of disease ; micro-organisms 

 may live and multiply in the plasma, and infect the whole body as in 

 anthrax. Some of the organisms may be so small as to be ultra- 



