576 IMMUNITY 



by Ehrlich and his co-workers in favour of a multiplicity of 

 complements are open to another interpretation ; the truth 

 probably lies between Ehrlich's and Bordet's views. Workers 

 of the French school also hold that complement does not exist 

 in the free condition in the blood, but is liberated from the 

 leucocytes when the blood is shed. This cannot be held as 

 proved. On the contrary, there are facts which are strongly in 

 support of the view that complement exists in the free condition 

 in the circulating blood. There is, however, evidence that the 

 amount of free complement increases after the blood is shed and 

 some time later gradually diminishes. 



The hemolytic action of a normal serum can be shown in many cases 

 to be of the same nature as that of an immune-serum, that is, comple- 

 ment and the homologue of an immune-body can be distinguished. For 

 example, guinea-pig's serum is hemolytic to ox's corpuscles ; if a portion 

 of serum be heated at 55° C, the complement will be destroyed ; if 

 another portion be treated with ox's corpuscles at 0° C, the natural 

 immune-body will be removed and only complement will he left. 

 Neither portion is in itself haemolytic, but this property becomes manifest 

 again when the two portions are mixed. Haemolytic sera are of great 

 service in the study of the question of specificity. Each is specific in the 

 sense already explained (p. 561), but the serum developed against the 

 corpuscles of an animal may have some action on those of an allied 

 species, that is, some receptors are common to the two species. This fact 

 can be readily shown by the usual absorption tests, for example, in the 

 case of an anti-ox serum tested on sheep's corpuscles. A close analogy 

 holds to what has been established in the case of agglutinins. It is 

 further of great interest to note that by the injection of red corpuscles 

 into an animal its serum not only becomes haemolytic, but in many cases 

 when heated at 55° C. possesses also agglutinating and opsonic properties 

 towards the red corpuscles used. These facts show how close an analogy 

 obtains between antibacterial and hemolytic sera, and how important a 

 bearing haemolytic studies have on the questions of immunity in general. 



In addition to haemolytic sera, anti-sera have been obtained by the 

 injection of leucocytes, spermatozoa, ciliated epithelium, liver cells, 

 nervous tissue, etc. The laws governing the production and properties 

 of these are identical, that is, each serum exhibits a specific property 

 towards the body used in its production — i.e., dissolves leucocytes, im- 

 mobilises spermatozoa, etc. The specificity is, however, not so marked 

 as in the case of sera produced against red blood corpuscles ; thus a serum 

 produced against tissue cells is often haemolytic ; this is probably due to 

 various cells of the body having the same receptors. Here again, when 

 the anti-serum produces no destructive effect on the corresponding cells, 

 the presence of an immune-body may be demonstrated by the increased 

 amount of complement which is taken up through its medium. It may 

 also be mentioned that each anti-serum usually exhibits toxic properties 

 towards the animal whose cells have been used in the injections, e.g. , a 

 haemolytic serum may produce a fatal result, with signs of extensive blood 

 destruction, hemoglobinuria, etc., i.e., it is haemotoxic for the particular 

 animal ; a serum prepared by injection of liver cells has been found to 

 produce on injection necrotic changes in the liver in the species of animal 



