122 PHYSIOLOGY OF YEASTS (Continued) 



ical similarities to cancer. The inoculation and rapid increase in loco 

 of these yeasts alone determine the common lesions exactly as in all 

 foreign bodies. According to Maffuci and Sirleo, many yeasts, which 

 have been isolated from malignant tumors, came from the air and 

 not from the diseased tissue. These authors have been able to isolate 

 yeasts from numerous carcinomas and sarcomas, 1 but they also ob- 

 tained them by exposing gelatin plates to the air of the laboratory. 



It then seems probable that many of the yeasts, said to have been 

 isolated from cancer tissue, really came from the air. 2 



It seems certain, however, that yeasts may be found in certain 

 malignant tumors, but they must be of only secondary importance in 

 the disease. They never cause it. The yeasts develop simply be- 

 cause they find the organism weak and in the neoplastic tissue a 

 favorable environment a good culture medium. One is able, for 

 example, to secure Endomyces albicans in certain tumors which, as 

 is generally known, causes an infection in infants, aged and gener- 

 ally "run-down " individuals. The blastomycelial theory of cancer 

 has been definitely rejected. 



Pathogenic Properties of Yeasts 



Even though it is admitted today that yeasts have no relation 

 to cancer, it is possible to inquire whether certain yeasts, either 

 special yeasts or common saprophytes, are not capable of present- 

 ing, at times, toxic or pathogenic properties. Generally speaking, 

 the question has been answered in the negative, and it is now rec- 

 ognized that the yeasts are almost without significance for the higher 

 animals. 



Rabinowitch, 3 in inoculating 50 varieties of ordinary yeasts into 

 various animals, found only seven which were pathogenic for the 

 mouse and rabbit. None caused even the slightest reaction in the 

 guinea pig. The animals which were killed seemed to be dead from 

 infection and not intoxication. Yeasts do not seem to secrete a toxin 

 which has any action on animals. 



The results of investigations conducted by Skchiwan 4 have shown 

 that yeasts have practically no chemiatric action towards leucocytes. 

 This was demonstrated by introducing S. pastorianus in capillary 

 tubes into the peritoneum of guinea pigs and rabbits. 



1 Guegen, F. Les Champignons Parasites de Thomme et des animaux. These 

 d'agr6g. de Pharmacie, Paris, 1902. 



2 Guiart, J. Precis de parasitologie. Baillierie edit. Paris, 1910. 



3 Rabinowitch, L. Untersuchungen iiber pathogene Hefearten. Zeitschr. 

 Hyg. 21, 1896. 



4 Skchiwan. Ann. Inst. Past. 8, 1890. 



