50 Lectures on Bacteria. [ vi. 



temperature between these extremes. The cardinal points of 

 temperature are accordingly distinguished as minimum, maxi- 

 mum, and optimum. 



Transgression of the limits leads at first to a cessation of the 

 particular process going on at the time ; other processes may 

 possibly persist. If the raising or lowering of the temperature 

 beyond the maximum or minimum point of vegetation reaches 

 certain extreme degrees, life is destroyed, in other words the 

 death-point is attained. 



In all these respects considerable variations occur in confor- 

 mity with every one's daily experience, according to the species, 

 the state of development, and the character of the environment. 



The limits of temperature in the growth and multiplication of 

 cells are the points which have been chiefly examined in the 

 case of the Bacteria ; it being assumed with some reason that 

 the rest of the vegetative processes, other conditions remaining 

 the same, run proportionally with the growth. 



It appears from the data before us that non-parasitic species, 

 if well and properly nourished, have a tolerably wide range and 

 a high optimum of growth-temperature. The former lies in 

 Bacillus subtilis, for example, according to Brefeld (19), between 

 6C. and 50 C., the optimum being at about 30 C. Bac- 

 terium Termo, Cohn grows between 5 C. and 40 C., while 

 its optimum is 30-35 C. (Eidam 20). Bacillus Amylobacter, 

 according to Fitz (21), has its optimum in solution of glycerine 

 at 40 C., its maximum at 45 C. The minimum of growth, 

 according to present accounts, in Bacillus Anthracis in cultures 

 in gelatine, on potatoes, &c., is at i5C., the maximum at 

 43 C., the optimum at 20-25 C. As a parasite in the blood 

 of rodents it grows at about 4 C. ; at least, not less vigorously 

 than in the optimum just given for specimens under culture. In 

 the Spirillum of Asiatic cholera, according to van Ermengen 

 (see Lecture XIII), the minimum is reached at 8C., the 

 optimum at 37 C., the maximum at 40 C. 



That the species which are more strictly adapted for a para- 



