8 A MANUAL OF VETERINARY PHYSIOLOGY 



means haemoglobin escapes from the cell. Snake venom and the 

 poison of bees and of certain spiders produce haemolysis, so also 

 some pathological toxins, of which the most noteworthy in the 

 horse is that producing so-called azoturia. The most remarkable 

 result is that obtained by adding to, or injecting into, the blood 

 of one animal the serum of an animal of a different species. 

 This leads in certain cases to destruction of the red cells, and a 

 chain of results of the highest practical importance. If, for 

 example, the fresh serum of the blood of the dog be added to the 

 washed red corpuscles of the rabbit, the latter are destroyed and 

 the colouring matter liberated. If the serum of the dog be 

 previously heated to 55 C. (132 F.), it may be added in any 

 quantity to the washed blood-cells of the rabbit, without pro- 

 ducing any effect on them ; evidently something has been 

 destroyed by the process of raising the temperature. This some- 

 thing can be restored by adding to the heated dog's serum some 

 serum which is not haemolytic for rabbit's cells (say rabbit serum). 

 The effect now is to render the dog's serum once more haemolytic. 



So far the phenomenon is physiological. The serum of any animal, 

 however, can be rendered haemolytic for the corpuscles of another 

 species by injecting the first with the red corpuscles of the second. 

 If, for example, the corpuscles of species A, say an ox, be injected 

 into species B, say a goat, the serum of the goat becomes actively 

 haemolytic for the corpuscles of the ox, and will cause haemoglobinuria 

 and death when inoculated to the latter animal. The goat's serum 

 will also haemolyse the corpuscles of the ox in vitro. If it be heated 

 to 55 C, however, it loses its haemolytic action, which can be 

 restored to it in the way mentioned above. The explanation is 

 that there are two substances in the haemolytic serum concerned in 

 the production of haemolysis. One is relatively unstable, and is 

 destroyed by a temperature of 55 ° C. This is the destroying agent, 

 which is known as the complement. The other substance is spoken 

 of as the immune body, the anti-body, the amboceptor, or substance 

 sensibilisatrice. It is not destroyed by a temperature below 65 ° C. 

 When a haemolytic serum is heated to 55 C. for half an hour, its 

 haemolytic action is lost, because the complement has been destroyed. 

 It can be restored by adding fresh, though non-haemolytic, serum 

 from another animal — a guinea-pig, for example — because the 

 complement is not specific, and is the same in all animals. If a 

 haemolytic serum be heated before injection to the animal, it still 

 causes haemolysis, because the complement is supplied by the 

 animal's serum. The immune body, on the other hand, is specific 

 for the corpuscles of the species against which it has been prepared, 

 and for those of no other. These phenomena are closely related 

 to the reaction of the body towards bacteria, and are concerned in 

 the production of antitoxins. 



Agglutination is the process by which the red blood-corpuscles 

 are collected together in clumps, under the influence of an agent 

 in the blood known as an agglutinin. Agglutination frequently pre- 

 cedes haemolysis, but it is independent of it, for if the complement 



