38 



The above are cases where the secondary pneumococci belonged 

 to one or other of the types with which sera have been prepared. 

 In some cases, strains, which have been proved bile soluble, 

 have been found accompanying or replacing the Types I or II, 

 and have not been serologically identified. In many of the 



3 when repeated examinations have been made, either the 

 original infecting strain has survived in a pure state, or no 

 pneumococci have been found. 



For example a sputum (Pn. 120) from a man aged 22 years yielded 

 eight colonies, all of which were Type II, on the sixth day of pneumonia : 



11 days after the crisis, six colonies were all Type II: 19 days after 

 the crisis, the sputum failed to infect a mouse. 



In another case, Pn. 146, tested before the crisis, Type I was found in 



12 colonies direct from the sputum and in 20 colonies through the mouse. 

 The sputum taken eight days later failed to infect a mouse. 



In a tliird case the sputum from a man aged 43 years yielded Type II 

 on the third day of pneumonia. During convalescence, 16 days later, a 

 second specimen was obtained which also yielded Type II only, 10 colonies 

 direct from the sputum and 1 through the mouse being examined. 



No decision can be made from these results on the relation- 

 si lip of the primary and secondary types of pneumococci in a 

 sputum. They emphasise the necessity of caution in deciding 

 on the type of infecting pneumococcUs, at least where the material 

 is not obtained direct from the diseased lung. 



Action of Culture and Pneumococcal Exudates 

 on Immune Serum. 



The American investigators have shown that the precipitate, 

 which results from mixing an immune serum with the culture 

 autolysate of the homologous pneumococcus, contains the pro- 

 tective substances of the serum. The possibility of obtaining a 

 therapeutic reagent in a concentrated form by this means was 

 considered by them, but it was found that the product of the 

 reaction was liable to be contaminated, and, moreover, the 

 protective properties were unstable. I have made some experi- 

 ments on the above lines, with a view to studying the mode of 

 action of a serum which has the property of protecting 

 mice against a subsequent inoculation of a virulent pneumo- 

 coccus. Many views have been put forward, but that of Neufeld 

 still holds the field, namely that the active substances in a pro- 

 tective serum are bacteriotropic, and are only available against 

 a type of pneumococcus similar to that which produced the scrum. 

 The results of the absorption tests given on page 41, in which 



• incut with the homologous pneumococcus removes the 

 protective power of the serum, afford some confirmation for this 

 view. There is, however, the possibility that the protective 

 sul .stances are carried down with the agglutinated cocci, and do 

 not actually adhere to them. 



The following experiment shows that a washed heated sus- 

 pension of pneumococci precipitates the protective substances 

 from a serum without impairing their properties. 



