CHAPTER IV 



Physiology of Fungi: Requirements for 

 Growth and Reproduction 



WHEN conditions are optimal, the vegetative portion of a fungus 

 increases and develops. If conditions are adverse, the fungus has 

 a tendency to produce spore forms, which are more resistant. The following 

 brief discussion presents some of the known extrinsic factors requisite for 

 the full development of fungi. 



The fungi classed as dermatophytes ( which are responsible for the super- 

 ficial infections) are usually found in relation to keratin, occurring in the 

 stratum corneum, in the substance of nails, in or on hairs or in the hair 

 follicles. This dermatropism has been subjected to scrutiny by a number of 

 investigators. The inability of these fungi to live or reproduce in the internal 

 organs and tissues is remarkable. Other fungi are able to invade the deeper 

 portions of the tissues and seldom, if ever, are found in superficial locations. 



1. TEMPERATURE 



Most pathogenic fungi grow well at room temperature and more vigor- 

 ouslv at body temperature. In the summer, fungi in culture develop more 

 rapidly and the character of the growth is different from that of the same 

 strain during the winter months. The counterpart in the clinical features 

 of fungous infections is well known. 



2. MOISTURE 



One of the factors thought to be important in predisposing toward 

 fungous infection of the toes is the moisture normally present or due to 

 lack of drying after a bath or other conditions. It is well known that in 

 culture, growth at low humidities is slow. The water requirements of 



