RENNET FERMENTS. 63 



According to Fermi, about one-third of the varieties investigated 

 possess the ability to form such ferment, but only on albuminous 

 nutrient media (A. H. xi, 1, and C. B. xil, 713). It is produced by 

 bacilli of the subtilis group (anthrax, megatherium, Fitzianus, etc.), 

 the vibriones related to the cholera vibrio; besides, Micrococcus 

 tetragenus, Micrococcus mastitidis, Bact. janthinum, Bact. mallei, 

 Bact. pyogenes foetidum, Bact. phosphoreseens, Bact. pneumonias, 

 Bact. synxanthum, Bact. aceticum. The remainder do not elaborate 

 it or it is doubtful whether they do. Besides, all actinomyces and 

 Oosporeae (with the exception of theOo. carnea) form such a ferment. 

 Most of these varieties afterward utilize the sugar further to form 

 acid, while others do not; for example, Bacillus subtilis. 



Inverting ferments i. e., such as convert cane-sugar 

 into grape-sugar are rare, according to Fermi and Mon- 

 tesano (C. B. L. i, 482). Their presence is easily dem- 

 onstrated by mixing a 1% to 2% solution of cane-sugar 

 containing carbolic acid and the culture treated with 1% 

 carbolic acid, and after a few hours testing with Fehling's 

 solution, and learning if it reduces the solution after stand- 

 ing, which cane-sugar admittedly does not. Control ex- 

 periments with a solution of cane-sugar alone are always 

 necessary. Fission fungi invertin can (always ?) stand 

 100 for over an hour; it is also produced in non-albu- 

 minous nutrient media, if glycerin is added. As producers 

 of inverting ferments the above authors mention only: 

 Bacillus megatherium, B. kiliense, B. fluorescens lique- 

 faciens, B. vulgare, and Vibrio cholerse and Metschnikovii. 



Efforts to find a ferment resembling emulsin have been 

 frustrated. The * ' Micrococcus pyogenes tenuis ' ' splits 

 off benzaldehyd from amygdalin, but without the function 

 being separated from cell-life. 



Rennet ferments i. e., bodies which coagulate milk 

 of neutral or amphoteric reaction, unconnected with the 

 action of acid are not lacking among the products of bac- 

 teria. For example, cultures of the Bact. prodigiosum, if 

 not too old, sterilized by heat at 55 to 60, cause a solid 

 coagulation of sterile milk in ope or a few days (Gorini, 

 C. B. xii, 666). 



Thorough investigations regarding the distribution of 

 this ferment are unknown to me. We may suspect it in 

 all varieties which coagulate milk without being able to 

 form lactic acid from milk-sugar. 



