272 F. JEFFREY BELL. 



although we have been with literature on the subject. Cohn's 

 discussion on " lasting spores " (Dauersporen) is really of in- 

 terest. He has already referred to the subject in his previous 

 essay ; there noting the great probability of Bacillus being 

 reproduced by gonidia or lasting spores, which had an oily 

 highly refractive internal substance ; three observers, Perty, 

 who called them Hygrocrocis, Trecul, who described them as 

 Urobacter, and Billroth, who gave them the name of Helo- 

 bacteria, had already observed these spores. Cohn having 

 carefully repeated Bastian's experiments,^ found that after 

 three or four days the fluid was troubled, not by B. termo, 

 but by Bacillus. Wondering, therefore, whether there were 

 not certain forms of these organisms which could withstand 

 the effects of boiling, he applied himself to what we will call 

 the natural history of cheese. 



23. Having observed the whole process, he thinks the 

 operation consists of three parts : 



(1.) The coagulation of the milk, which, as he says, is due 

 not to organised, but merely to non-organised ferments 

 (chymosin), comparable in action to diastase and pepsin. 



(2.) The separation of the coagulated casein from the whey, 

 which is a purely mechanical process, comparable to the 

 separation of butter from milk, or fibrin from blood. 



(3.) The coming to maturity of the cheese, which is a true 

 fermentation, caused by ferment organisms (Zymophytes), 

 accompanied by the evolution of gases and the formation of 

 spaces, as in bread ; the heat which is applied (55 — 60°) kills 

 B. termo, and appears to leave free play for the activity of 

 the peculiar ferment organisms of the cheese. 



24. The Bacilli, represented in figs. 6 — 8, were more 

 closely studied in the laboratory at Breslau ; they were 

 obtained from the rennet of a calf, of five to seven weeks old. 

 It was found that their activity was lessened at 50° C, but 

 below 30° was destroyed ; they were seen to be actively 

 moving, long, fine Bacilli, ordinarily paired, but sometimes 

 united by fours or eights, never absent from the extract of 

 the rennet. They are probably found in the living stomach, 

 and such forms have, indeed, been already observed by 

 Remak (1845) and Wedl (1858); they also appear to be the 

 same as Pasteur's B. subtilis, which are so remarkable for 

 their resistance to high temperatures, as well as for their 

 activity in air deprived of its oxygen. If the fluid in which 

 these are found be kept for some time at 30°, there are to 

 be observed fibres with a swollen extremity, filled with oval 

 slightly refractive granules,which, closely resemble in form the 



• 'Proc. Royal Soc.,' 1873, No. U5. 



