SHAPE OF MICROORGANISMS 



35 



toward the bacteria which are invading the body of the individual 

 who is suffering with boils. 



Molds, — ^The body of a mold is composed of numerous cells, 

 whereas the bodies of bacteria and yeasts are single cells. The 

 thread-like processes which compose their body are known as 

 mycelia (singular, mycelium). The individual threads are called 

 hyphae. In the molds 

 there is a division of la- 

 bor. Some threads serve 

 for the taking up of nu- 

 trients and are called 

 vegetative hyphae/ the 

 Others produce spores, 

 fertile hyphae. The cells 

 composing the molds are 

 similar to those of the 

 yeasts in that they have a 

 definite nucleus. They 

 multiply mainly by the 

 production of spores 

 which are produced in the 

 fertile hyphae* above the 

 surface of the medium 



and hence can be dislodged and spread by currents of air. They 

 grow under conditions of acidity and moisture which are inimical 

 to the growth of bacteria and yeasts. They differ from bacteria 

 in that they all require free oxygen. They play a great part in 

 the spoilage of foods and are second only to bacteria in impor- 

 tance in soil processes. Few are pathogenic. More of the molds 

 than of the yeasts produce diseases in man and the lower animals. 



Fig. 20. — Dra^^ving of a mold colony. 



