PNEUMOCOCCAL VACCINES 487 



antibodies. In this connection there may be also mentioned the in- 

 tradermal injection in the treatment of lobar pneumonia of "natu- 

 ral bacterial antigens" prepared from living pneumococci by the 

 addition of Merthiolate, as reported by Sutton, Kendall, and Ro- 

 senblum (1931). 1868 The results invite further study of the desir- 

 ability of the skin as a locus for the administration of pneumococ- 

 cal antigens. 



That a certain degree of specific immunity in rats may follow 

 the ingestion of pneumococcal derivatives has been shown by Mc- 

 Daniels, 876 among others, who, as a preparatory measure, fed egg- 

 white to the animals thirty minutes previous to the oral admin- 

 istration of antigen. Animals receiving the preliminary dose of 

 egg-white exhibited greater resistance than did the controls to a 

 subsequent intraperitoneal injection of graded amounts of a viru- 

 lent culture of pneumococci of homologous type. 



In a series of communications extending over the period from 

 1925 to 1934, Ross 1178 " 94 reported the results of studies on the im- 

 munizing effect of feeding several different forms of pneumococcal 

 material first to rats and subsequently to man. In some of the au- 

 thor's early experiments it was found that the ingestion of soluble 

 specific substance from Type I pneumococci induced in the rat ac- 

 tive immunity of homologous type, and a similar condition ensued 

 after feeding the animals with filtrates obtained from pneumo- 

 cocci dissolved by bile salts. The degree of immunity following the 

 administration of the polysaccharide appeared to be greater than 

 that developing when suspensions of the intact cell were employed. 

 In the case of Type II polysaccharide the animals acquired little 

 or no immunity, but with Type III carbohydrate the effect, though 

 slight, was type-specific. Ross noted that a large part of the poly- 

 saccharide administered orally passes through the alimentary 

 tract practically unchanged as far as antigenicity is concerned 

 but, strange to say, he could not detect the substance in the blood 

 of the treated animals. 



In his later publications, Ross reported the appearance of spe- 



