MOULDS 319 



associated with, or the cause of, various morbid processes. 

 In some instances this is seen only in animals. This cir- 

 cumstance does not strictly show that such moulds are 

 pathogenic for man ; but it is certainly difficult to establish 

 strictly that they are not pathogenic, and as the conditions 

 of moisture, etc., which usually ' favour their growth are 

 insanitary, their presence should be taken to indicate in- 

 sanitary conditions. The moulds form spores, and, like 

 the bacteria proper, are remarkable for the great resistance 

 they offer to external influences, and which under favour- 

 able conditions, such as moisture, warmth, and nourish- 

 ment, develop into complete individuals. 



The spores, or conidia, as they are called, shoot off little 

 buds, which lengthen at the end by fission, giving rise to 

 a long thread of cylindrical cells, which sometimes branch, 

 forming a freely-growing network of fibres known as mycelia. 



The heads of these mycelia then form spherical or oval 

 cells, which are the seed-bearing organs known as the 

 liyphcB or thallus. It is from these organs that the moulds 

 derive their name of hypomycetes. Some hyphse form 

 large round or cylindrical mother-cells, or sporangia, in 

 the interior of which spores are formed by endogenous 

 formation. According to the form of the seed-bearing 

 organ, the moulds are divided into four divisions, viz., 

 MucorinecB, Aspergillince, Penicilliacece, Oidiacece. 



1. Mucorineae. — In the mucors, or headed moulds, the ends 

 of the hyphsB swell into knobs known as columella, around 

 which a seed-capsule or sporangium forms. When ripe, the 

 spores burst the enclosing membrane, and thus become free. 



2. Aspergillinse. — The Aspergillinse, or knob-moulds, have 

 hyphsB, the heads of which are covered with a number of 

 spores, carriers, or sterigmata, from the extremities of which 

 the spores divide off into rows. 



3. Penicilliaceae. — The Penicilliacese, or pencil moulds. 



