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Scientific Proceedings (131) 



from the plausibility of the assumption that there is one. Until 

 the presence of such a vitamin is established in natural infants' 

 diets in cases where rickets is prevented and a deficiency in diets 

 of cases where rickets occurs it will be safer to approach the 

 subject with an open mind. The rickets-curing substances in 

 cod liver oil and in egg yolk might just as well be looked upon 

 as therapeutic agents, possibly internal secretions, which will 

 prevent or cure rickets. 



182 (2142) 



On the nature of pneumococcus antigen. 

 By W. A. PERLZWEIG and G. I. STEFFEN (by invitation.) 



[From the Hygienic Laboratory of the U. S. Public Health Service 

 and the Second Medical (Cornell) Division and the Patho- 

 logical Department of Bellevue Hospital, New York City.] 



Various extracts of killed pneumococci have been studied for 

 the purpose of determining their immunizing power and their 

 freedom from toxic products. A non-toxic pneumococcus anti- 

 gen of high potency can be made by suspending the sediment 

 from a centrifuged pneumococcus broth culture in saline and 

 digesting the pneumococci with 0.2 per cent, trypsin for 24 to 

 48 hours. The undigested portion is centrifuged off and the 

 metaproteins in the supernatant fluid precipitated with acid. 

 After filtration the filtrate is thrown into 7 volumes of 95 per 

 cent, alcohol, the resulting precipitate filtered off and the alcoholic 

 solution evaporated in vacuum. The residue in the flask is taken 

 up in saline and made up to the original volume of the saline 

 suspension. This solution contains the immunizing antigen of 

 the pneumococcus. Mice which had received three subcutaneous 

 injections of this antigen were protected against a hundred thou- 

 sand lethal doses of a pneumococcus broth culture, injected in- 

 traperitoneally. 



Human volunteers were injected subcutaneously with the 

 alcohol soluble fractions of pneumococcus Type I, II, and III. 



