408 Mr. G. Dean. Enquiry into the Nature of the [Apr. 23, 



All were brought to the same volume. 



A repetition of Experiments 3, 4, and 5, with a thinner emulsion of the 

 typhoid bacillus, gave the relation 0*9, 2*0, and 3*6. 



These experiments show, in the case of the sera of the rabbit and of the 

 guinea-pig in relation to the typhoid bacillus, a marked parallelism between 

 the extra-corpuscular bacteriolytic function and the sensitising or opsonising- 

 function by means of which the organisms are prepared for phagocytosis, 

 and that a complementary action takes place in both cases. 



The Indirect Method. 



These experiments were based on the observations made by Ehrlich r 

 Morgenroth, Bordet, PfeifTer, and others that the injection of the serum of 

 one species into another gives rise to the elaboration in the blood of the latter 

 of anti-bodies, which may act either on the amboceptor or on the complement. 

 Anti-complement formation is a common phenomenon, Whereas anti- 

 amboceptor is of rare occurrence. The mechanism of the action of such sera, 

 has been the subject of much discussion which cannot be touched on here. 

 In the present paper the term " anti-complement serum " will be used without 

 prejudice, the possibility that such a serum may act on other bodies besides- 

 complement not being overlooked. In relation to the present subject, it 

 seemed of interest and importance to ascertain the effect produced by an 

 anti-complement serum in experiments of the type of these with which we 

 are dealing. Whilst these experiments were in progress, Muir (1906) pub- 

 lished results obtained by a similar method with which, in the main, the 

 present series are in agreement. 



Technique Employed. 



The anti-complement serum was prepared by injecting a rabbit on several 

 occasions with human or horse serum which was previously heated to 

 58° to 60° C. for half an hour. The anti-complement serum, after separation, 

 was itself heated to 60° C. for 20 minutes. Varying proportions of this, 

 serum were then added to the homologous fresh serum, or to the mixture of 

 which it was a constituent part. The tubes containing these were incubated 

 for two hours at 35°*5 C. In this way a precipitin reaction was produced. 

 The supernatant fluid removed from the precipitum was employed in the 

 experiment. By doing a series of eight or 12 such tests, the most effective 

 combinations of the serum were ascertained. In some of the experiments 

 there was no such preliminary treatment of the fresh serum by the anti- 

 serum, this being simply made one of the constituent parts of the mixture of 



