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An Experimental Enquiry into the Nature of the Substance 

 in Serum ivhich influences Phagocytosis. 



(Second Communication.) 

 By Geokge Dean, M.A., CM., M.B., Chief Bacteriologist, Lister Institute. . 



(Communicated by Dr. C. J. Martin, F.E.S. Eeceived April 23, — Read 



May 30, 1907.) 



In a previous communication it was shown that in certain immune sera, 

 e.g., in anti-staphylococcus, in anti-dysentery, and in anti-typhoid serum, there 

 are present thermostable substances which, by their action, prepare the 

 homologous organisms for phagocytosis. The thermostability in the case of 

 these immune sera could be demonstrated by the use of Wright and Douglas' 

 method, whereas in the case of normal serum another method was, as a rule, 

 necessary. In the case of the serum of the horse, however, it was pointed 

 out that even by Wright and Douglas' method the increase of phagocytosis, 

 observed by using normal heated serum, was, as compared with salt solution, 

 generally considerable. 



In view of certain experimental data and having regard to Ehrliclrs theory, 

 the conclusion was arrived at that the thermostable substances of normal and 

 immune sera were probably identical. 



It was further shown that, when submitted to a temperature of 60° C, both 

 immune and normal serum suffered a rapid and sudden diminution in opsonic 

 power. This change occurs in the first few minutes of heating, after which 

 further loss appears to take place very slowly. 



The results obtained suggested that the sensitising action of the serum 

 might be due to the combined action of two substances, the one thermostable, 

 the other thermolabile ; the one of the nature of the " substance sensibilisatrice." 

 the other of the nature of an alexin. 



The present paper is an account of certain experiments carried out with the 

 view of elucidating this point:* 



* In the course of writing this paper, a communication by Neuf eld and Hiine has reached 

 me, in which, in a criticism of my interpretation of these curves, they appear to have 

 overlooked the fact that I had indicated the possibility that the sudden fall may be due to 

 a destruction of complement. As at the time of the publication of my previous com- 

 munication I had no experimental data to support that view, I preferred to leave the 

 matter for further investigation. What I said was : 



" Whether free complement may take part in the preparation of the microbe is difficult 

 to determine. From the experiments detailed in this paper it is certain that it is not a 

 necessary participant in this action. At the same time it is not improbable that the 



2 G 2 



