90 THE FEEDING OF ANIMALS 



kingdom. As a rule, each individual plant is a single 

 cell and so minute as to be invisible to the unaided sight. 

 It corresponds in its general structure to the cells which 

 make up the tissues of the higher vegetable species, i. e., 

 it consists of a cell wall inside of which are protoplasm 

 and other forms of matter. These organisms are dis- 

 tributed everywhere in the air, in the soil, on surfaces 

 of plants, and in the bodies of animals. Whenever the 

 right opportunity offers itself, they multiply and bring 

 about all the results attendant upon their growth. 



124. Conditions of growth of organized ferments. 

 The conditions essential to their development are the 

 proper degree of moisture and temperature and the neces- 

 sary food materials. Animal and vegetable substances 

 supply the necessary nutrients, but when thoroughly dry 

 do not ferment. Flour and meal that have been dried to 

 a water-content of 10 per cent will keep a long time with- 

 out loss from fermentative changes. The heat in a mow 

 of hay or in a bin of new grain, with their subsequent 

 musty condition, is due to the fermentations that are 

 made possible through the presence of considerable 

 moisture. Thorough drying is a preventive of these 

 destructive fermentations. 



There is a temperature at which each vegetable ferment 

 thrives best, and there are limits of temperature outside 

 of which the growth of these forms of life does not occur, 

 or is very slight. Numerous species thrive between 75 and 

 100 F. Fermentable materials like fruit and meat at 

 the freezing-point or below are not subject to fermenta- 

 tions. The boiling-point of water kills most bacteria, 

 and temperatures above 150 F. retard or entirely pre- 

 vent their growth. 



