350 BIOLOGY OF PNEUMOCOCCUS 



animals against Type I organisms. An observation of Ross on the 

 fate of the ingested polysaccharide was that a very large propor- 

 tion of the substance, when fed to rats, appeared in the feces. 



Further experiments on oral immunization against Pneumococ- 

 cus, when applied to rabbits, were described in 1932 by Kolmer and 

 Rule. 745 The antigens comprised a) pneumococci of Types I, II, 

 and III cultivated in sterile milk for twenty-four hours and heated 

 at 60° for one hour, b) twenty-four-hour broth cultures of the 

 same types exposed for two hours to a N/15 concentration of hy- 

 drochloric acid, and c) sedimented cocci from twenty-four-hour 

 broth cultures subsequently treated with sodium taurocholate. The 

 materials were administered daily for seven days through a stom- 

 ach tube, and one week after the last treatment the rabbits were 

 inoculated intratracheally with living broth cultures. While to 

 Kolmer and Rule the acid-killed cocci, of the three kinds of prepa- 

 rations used, appeared to engender the highest degree of immu- 

 nity, the figures are not significant because of the lack of uni- 

 formity of the results and the low virulence of the Type II and 

 Type III cultures employed in testing the resistance of the rabbits. 



In a second report (1933), Kolmer and Rule 747 stated that the 

 oral administration of acid-killed vaccines made from Type I, II, 

 and III pneumococci, in doses representing 100 to 1,000 million or- 

 ganisms per kilo of body weight, were effective in rendering rabbits 

 immune to subsequent intratracheal infection with pneumococci of 

 the homologous type. Although occasionally a single dose of 1,000 

 million cocci produced active immunity against infection by Type 

 I Pneumococcus, the best results were obtained with a minimum of 

 five daily doses. The immunity thus induced was transient, de- 

 creasing after one month's time and practically disappearing in 

 six months. Vaccines introduced by way of the mouth were inferior 

 in immunizing action to similar agents injected subcutaneously. 

 Using monkeys as test animals, and employing vaccines of pneumo- 

 cocci killed by tricresol and by hydrochloric acid, Kolmer and 



