PHAGOCYTOSIS 28l 



taken up, and in some cases digested, within a few minutes. In 

 the body, of course, the action may go on for hours. The opsonin- 

 leucocyte mechanism would appear far stronger than is necessary 

 for the defence of the body. That it is not so indicates some 

 fallacy in the conclusions to be derived from these experiments 

 in vitro. We shall revert to this subject subsequently, and in the 

 meantime be content with pointing out that where a very small 

 amount of opsonin would appear sufficient for the resources of 

 the body, but little importance can be attached to small fluctua- 

 tions, or to a rise, e.g., from 0-8 to i. 



The dread of a low opsonic index appears to have arisen on 

 purely theoretical grounds, and the only direct research on the 

 subject which seems to have been undertaken points rather in the 

 other direction. According to Pfeiffer and Friedberger, guinea- 

 pigs injected with bacterial vaccines (typhoid and cholera) do not 

 thereby become hypersensitive to doses of living cultures given 

 twelve or thirty-six hours afterwards ; on the contrary, they have 

 acquired an increased power of resistance, even after the shorter 

 period. And a very remarkable fact was noticed : this increased 

 resistance was not specific, since animals injected with heated 

 typhoid bacilli survived a lethal dose of cholera as well as of 

 typhoid. They conclude that the fear of a negative phase is 

 exaggerated ; and it must not be forgotten that the essence of 

 the " opsonin therapy " consists in administering a dose of vaccine, 

 in the first instance, while the index is low. 



There is thus no direct proof that the period of the negative 

 phase is coincident with the period of hypersensitiveness to 

 infection. And when we compare it with the period of increased 

 sensitiveness to toxins, we find that, whereas the negative phase 

 comes on almost immediately, the hypersensitiveness to toxins 

 or tuberculin, or anaphylaxis to serum, takes some days to 

 develop. 



Other theoretical interpretations of the undoubted good effects 

 of vaccine therapy are possible. Thus, a very probable explana- 

 tion is that it causes a local reaction in the form of an aseptic 

 inflammatory process in the neighbourhood of the lesion, which, 

 like the similar reaction caused by ultra-violet or X rays, has (in 

 some way not yet understood) a curative effect. The nature of 

 these " reactions " is considered subsequently ; in the meantime 

 it is sufficient to say that in the case of tubercle (and it is 

 probably a general effect) an injection of dead bacilli, or of the 



