r 



YEASTS AND MOULDS. 233 



the protrusion of a little bud from the cell, which develops 

 into a new cell. In an actively germinating growth of yeast 

 these budding cells are readily distinguished (Fig. 52). 



Yeasts have been found that were pathogenic to animals. 

 They have also been supposed to be the cause of some 

 malignant tumors, but this view has been, for the most part, 

 abandoned. 



Among the moulds the varieties most commonly en- 

 countered are the mucor, the penicillium, the aspergillus 

 and the oidlum. There are various species of each of 

 them. They consist of cells arranged end to end, making 

 a thread-like body called a hypha. The threads are matted 

 together and form a mycelium. Certain threads project 

 upward from the mycelium, and on them are borne spores, 

 or conidia. The arrangement of the spores is characteristic 

 in each variety of mould (Fig. 53). A group of organisms 

 exist which have affinities both with yeasts and mould- 

 fungi. Some of them are pathogenic. The form of infec- 

 tion of the mouth called thrush, is due to a fungus of this 

 class, which is generally considered an oidium. A chronic 

 inflammatory affection of the skin (blastomycetic der- 

 matitis) is due to related organisms. 1 The Sporotricha of 

 Schenck 2 which produces chronic subcutaneous abscesses, 

 may be mentioned here, provisionally. A number of skin 

 affections, such as Tinea favosa and Tinea trichophytina, 

 are due to fungi, which have some similarity with those 

 above mentioned. 



Among the mould fungi, several species of aspergillus and 

 of mucor are pathogenic. Man, as well as the lower ani- 

 mals, may be affected. In man the lungs may be involved 

 in a broncho-pneumonia (pneumonomycosis), usually due to 



'Ricketts, Journal of Medical Research, Vol. VI., 1901; Hyde and 

 Montgomery, Journal American Medical Association, June 7, 1902. 

 2 Hektoen, Journal Experimental Medicine, Vol. V. 



