CHAPTER XXXIX. 



BLASTOMYCES EPIZOOTIC LYMPHANGITIS IN HORSES 

 BLASTOMYCOTIC DERMATITIS. 



BLASTOMYCES. 



THERE is a large class of low vegetable microorganisms of which 

 the common brewer's and baker's yeast are the best-known types. 

 A few of these have been found as the cause of disease in man and 

 the lower animals. The classification of these fungi has been very 

 difficult, and botanically they have been defined as ascomycetes, 

 because, like these, they generally form a number of endogenous 

 spores in a spore sac or ascus. Yeast cells, however, frequently 

 present themselves as simple, more or less globular, strictly unicellular 

 organisms, and in them the whole cell becomes the ascus, or spore 

 sac, in which the endogenous ascospores are formed. As Lafar has 

 pointed out, the term saccharomyces (often improperly used in path- 

 ology) should be reserved for the sugar-fermenting organisms of this 

 type, since the word means sugar fungi. On the other hand, certain 

 organisms of this class have never been known to form spores, and 

 they cannot consistently be classified as ascomycetes. It appears, 

 however, that they have the common property of forming buds, i. e., 

 one or more nipple- or sac-like or globular offshoots or out-growths, 

 which later become separated from the main portion by a partition 

 wall or septum, drop off and form new independent unicellular 

 organisms. This process of multiplication is known as budding, hence 

 the organisms which show this mode of multiplication are known as 

 blastomycetes, or budding fungi. Most of the latter can also multiply 

 by sporulation, because they form more than one spore up to eight 

 and higher. Those blastomycetes which do not form spores are 

 grouped under the genus Torula. 



When blastomycetes are budding the newly formed buds are not 

 always necessarily cut off, so that the unicellular type is preserved. 

 Under some conditions both the mother cell and the bud elongate, 

 become elliptical or cylindrical, and adhere together. The process is 

 repeated a number of times at the outer ends of the connected cells, 

 and there are formed in this manner filaments and, indeed, a structure 

 with branching effects much like the mycelia of the hyphomycetes. 

 It has been ascertained that the saccharomycetes and probably the 

 blastomycetes in general possess a nucleus with a nuclear membrane 

 and nucleolus. These structures can only be seen exceptionally in 



