200 CLINICAL FAILURE OF BACTERICIDAL SERA 



These sera, which for the purpose of convenience we shall 

 consider together as if they were all bactericidal, are in general 

 protective, but not curative. Thus the clinical use of antityphoid 

 and anticholera serum has shown them to be quite worthless or 

 even dangerous ; dysentery serum is of distinct value if used 

 early in the attack, and some of the other sera are of some value, 

 and their use is discussed in the final section of this book. In 

 general terms, however, and comparing them with diphtheria 

 antitoxin, we may say that they have proved most disappointing 

 in practice. The reason for this failure requires some discussion. 



Antibacterial sera as ordinarily used are, of course, devoid of 

 complement, which has usually disappeared long before use ; it 

 is rendered inert on keeping, and is especially susceptible to the 

 antiseptics commonly added as a preservative. The first sugges- 

 tion is that the failure of the serum is due to lack of complement : 

 the union of the amboceptor and bacterium is supposed to take 

 place as usual, but the necessary alexin is not forthcoming. This 

 may be due to one of two causes : in the first place, there may be 

 (as is known to occur in certain diseases) a deficiency in the 

 amount of complement in the serum; in the second place, that 

 which is there may be unsuitable in nature. 



As regards deficiency in complement, this has been found to 

 occur in certain diseases, and is very probably a common occur- 

 rence in pathological conditions and states of malnutrition in 

 general ; but when we consider the comparatively small amount 

 necessary to activate a large dose of sensitized bacilli, there is no 

 reason to think that it ever falls below that level. Again, the 

 facts known concerning the immunity of the dog and other 

 animals to anthrax are of such a nature as to render it improbable 

 (in this case, at least) that deficiency of complement can really 

 be of much importance ; for dog's serum contains abundance of 

 amboceptor, yet no suitable complement, and is devoid of bacteri- 

 cidal action. We shall see reasons for believing that amboceptor 

 may possibly act as opsonin, in some cases at least, without the 

 concurrence of complement, and this is probably the explanation 

 of the immunity of the dog to anthrax. 



The other explanation, that of Ehrlich, is that the complements 

 present in human serum may be unsuitable to reactivate serum 

 derived from a horse, ass, or goat, or other animal used as the 

 source of the immune body. To obviate this, he has proposed 

 the use of sera from several species of animals, in the hope of 



