PATHOGENICITY FOR EXPERIMENTAL ANIMALS 187 



cocci and, while cold, avitaminosis, and pregnancy had previously 

 been shown to diminish resistance of guinea pigs, the authors con- 

 cluded that higher susceptibility was apparently of a more obscure 

 nature and was associated, as earlier suggested by Uchida, 1432 with 

 basic or temporary variations in the disposition of individual ani- 

 mals. A possible explanation for some of the constitutional differ- 

 ences in the susceptibility of guinea pigs is to be found in the com- 

 munication of Nicholls and Spaeth (1922), 1005 according to whom 

 there is a definite correlation between pigmentation and resistance 

 to infection. White-coated, pink-eyed guinea pigs, probably pure 

 albinos, were found to be far more susceptible to a given Type I 

 culture than were pigmented individuals. It seems unlikely that 

 pigmentation of itself was responsible for the resistance, although 

 it may well have been associated with the true cause. Uchida, 1431 

 who earlier had isolated pneumococci from guinea pigs suffering 

 from spontaneous infection, noted irregularities in the results fol- 

 lowing the subsequent subcutaneous, intraperitoneal, and intraven- 

 ous injection of the strains into normal guinea pigs. The author 

 assumed that the discrepancies in the outcome of the experiments 

 were due to varying degrees of resistance possessed by the indi- 

 vidual animals, but offered no specific explanation for the differ- 

 ences. 



Wamoscher (1927) 1479 observed that scurvy and chronic tuber- 

 culosis in the guinea pig were diatheses favoring spontaneous pneu- 

 mococcal infection. These and similar debilitating conditions may 

 likewise lower resistance to experimental infection. Schmidt-Wey- 

 land and Koltzsch* found that scorbutic guinea pigs could easily 

 be infected when pneumococci were introduced into the body by in- 

 halation or feeding. 



THE MOUSE 



The white races of the mouse family, because of low cost, ease of 

 handling, great susceptibility, and general uniformity of reaction, 



* Quoted by Neufeld and Schnitzer. 



