ALCOHOLIC FERMENTS. 219 



shape as the mother-cells, and surrounded by a membrane 

 with a distinctly double contour ; they number from 1 to 4 in 

 each cell, generally, however, only 2 ; they rather quickly 

 detach themselves, and the membrane of the mother-cell 

 then appears to be dissolved. The germination of the spores 

 appears to take place only in the stomach of animals. 1 



A yeast species or variety is called a " culture yeast " if 

 used industrially after a methodical selection made with special 

 considerations in view. Many culture-yeasts exhibit micro- 

 scopical differences from the " wild " yeasts occurring in the 

 same branch of industry, as pointed out with regard to the 

 construction of the spores. 



The different races or species of yeast may be divided into 

 two groups, according to the kind of fermentation to which 

 they give rise, viz, bottom-yeasts and top -yeasts. In spite of 

 many assertions to the contrary, it has not hitherto proved 

 possible to bring about an actual conversion of top-yeast into 

 bottom-yeast, or vice versa. The investigations of HANSEN 

 and KUEHLE show that it is certainly possible for a bottom- 

 fermentation yeast to produce transitory top -fermentation 

 phenomena ; these, however, quickly disappear with the pro- 



1 Concerning the behaviour of yeasts towards the human and animal economy, 

 work has recently been carried out with pure cultures. SIMANOWSKY had 

 pointed out that yeast in turbid beers may interfere with gastric and pan- 

 creatic digestion, and that such beers cause catarrh in the intestinal canal. 

 NEUMEYER found that the yeasts examined by him were very resistant to the 

 digestive juices, and could pass through the human and animal intestinal canal 

 without being killed. If introduced into the intestinal canal without ferment- 

 able substances, neither culture-yeast nor wild yeast exercised any action ; but 

 when introduced along with sugar-solutions, in which they were able to pro- 

 duce a vigorous fermentation, they all of them caused stomachic and intestinal 

 catarrh. This effect, according to NEUMEYER, is due to the fact that yeast, 

 during its development at the high temperature of the body, secretes abnormal 

 fermentation products which exert an injurious action upon the mucous 

 coating of the intestinal canal. Recent experiments by FERMI and L. RABINO- 

 WITSCH have shown that yeasts exist which develop and multiply freely in 

 the tissues on subcutaneous inoculation, and are capable of causing diseases 

 which often end fatally. These species botanically should be classed with 

 the so-called wild yeasts. Certain Monilia species have likewise proved to 

 possess pathogenic properties. 



