(■,i-:kM':ral coxsihi'.raikix oi.- nish'.Asi-;. 



51 



manure, etc., and they maintain their vitality in the dormant 

 state for a considerable length of time. 



The source of infection is contaminated fnod, water or air. 



The principal lesions are located in the trachea, bronchi, 

 lung and air cells of bones. The disease is characterized by a 

 fibrinopurulent intlammatiim of the mucous membranes of the 

 trachea and bronchi and aljscess formati(.)n in the King. 



AspcrgiHiits Nic/cr is probably responsible for the cause of 

 some cases of ear canker in dogs. 



Saccharomyces. (Yeast). 



Saccharom^'ces are the Imdding fungi. The classification of 

 this group, the \east plants, is as \-et incomjilete, their general 

 biologic characteristics not being well known. A few varieties, 



Fig. -0. — Yeast ( SLiueharuniyccs Far 



however, have been studied, one of which, Saccharomyces Cere- 

 visiae, is of considerable economic importance to the brewers. ^ 



Yeasts are ovoid or spherical single celled non-chlorophyllic 

 plants that reproduce by budding. Structurally the yeast cell 

 has a cell body composed of protoplasm and a double cell mem- 

 brane the latter composed of condensed protoplasm. The cell 

 body may contain vacuoles, granules or foreign substances. 

 Reproduction, which is bv budding or gemmation, occurs at one 

 or both ends of the veast cell and even in some cases from 

 the side of the cell. Budding begins by the appearance of small 

 tubercles or buds which develop until a considerable size is 

 attained. The daughter cell may remain associated with, the 



