CLASSIFICATION OF PNEUMOCOCCI 121 



the complication arising from a latent mouse-typhoid infection in 

 the test animals.* 



Sutliff's 1359 experience emphasized the apparent errors which 

 may occur when the testing of sputum by the mouse method is 

 taken as the only diagnostic criterion. He compared the results of 

 the protection test with those obtained by other cultural methods 

 or, in other words, checked the type of Pneumococcus found in the 

 sputum with the type or types isolated from the same patient by 

 means of blood cultures, from post-mortem lung cultures, and from 

 miscellaneous exudates. Among eighty-one cases in which Group 

 IV strains were found in the sputum, twelve showed the presence 

 of pneumococci of one of the fixed types in cultures obtained from 

 the blood or lung. This error of 14.8 per cent is significant. Sut- 

 liff demonstrated the advantage in performing a type determina- 

 tion on cultures isolated from the hearts' blood of the test mice 

 as well as on those from the peritoneal exudates. In 1,326 such 

 examinations, the outcome was positive in fifty-five instances with 

 the hearts' blood where the peritoneal exudate was negative. More- 

 over, Sutliff at times recovered two types of pneumococci from the 

 same mouse. Of 339 cases where the peritoneal exudate showed a 

 fixed type, the hearts' blood of the same test animals in fifteen, 

 or 4.4 per cent of these instances, yielded an organism of Group 

 IV and, in five, or 1.5 per cent of cases, pneumococci of a dif- 

 ferent specific type. In 862 cases in which the peritoneum of the 

 mouse yielded a Type IV organism, the hearts' blood showed fixed 

 types in thirty-one cases, or 3.6 per cent. Sutliff then, in all cases 

 showing Group IV pneumococci in the sputum, collected and ex- 

 amined a second specimen by the mouse method and here the same 

 discrepancy held. Of 145 cases, twenty-two gave results on the sec- 

 ond determination inconsistent with those of the first. Sutliff's ex- 

 perience prompted him to advise that "When a specific type of 



* Faber,378 feeling that a substitute for mice was needed, recommended rab- 

 bits, but it is feared that he failed to appreciate the economic aspects of such a 

 substitution. 



