INHIBITORY MEANS. 649 



temperature, &c. by the employment of which we might 

 be able for a certain time to neutralise the superiority of 

 the pathogenic bacteria over the cells of the animal body. 



The cessation of all vital phenomena, and also of Complete 

 growth and multiplication, is only brought about by development, 

 marked abnormalities in the external conditions. A 

 partial interference with growth is produced by all those 

 alterations in the conditions of existence which lead to 

 a departure from the optimum. These most favourable 

 conditions of existence have been referred to already in 

 detail, and it has also been pointed out in what way 

 every variation of temperature, concentration, &c., 

 beyond a certain limit results in interference with the 

 vital energy of the fungi. 



Complete cessation of growth frequently occurs as the Withdrawal 

 result of gradual exhaustion of the nutrient materials. nutrient Sary 

 In every nutrient medium it ultimately happens, as the materials, 

 result of continued multiplication of the fungi, that 

 some or all of the colonies no longer find the nutrient 

 materials necessary for their further development. In 

 fluids the yeast or fission fungi which have already 

 formed are deposited in the form of a powdery precipi- 

 tate on the bottom of the vessel. It depends chiefly on 

 the species of the fungus in question how long they can 

 retain their vitality under such conditions without a 

 fresh supply of nutriment. Some only exist in a latent 

 condition for a short time, they soon degenerate and 

 break up ; others are much more resisting. To the 

 first group belong the majority of the micrococci, to the 

 latter the spore-forming bacilli, the spores of which 

 can retain their vitality for years ; but many micrococci 

 also for example, Staphylococcus aureus show a 

 similar resisting power. It is not necessary that all 

 the nutrient materials should be exhausted ; on the con- 

 trary, the loss of a single necessary material is sufficient 

 to lead to a period of rest. 



A very frequent cause of cessation of the growth of withdrawal 

 bacteria is the diminution of the necessary amount of of water - 

 water in the nutrient medium. Growth ceases on the 

 most various nutrient media on the surface of the soil, 



