PLANT PARASITES. 159 



tion is to twist a small wad of absorbent cotton on to the end of an iron or steel wire 

 about five inches long, put this, swab end foremost, into the tube (Fig. 83), plug the 

 mouth with cotton, and sterilize the whole in a dry oven for an hour at 1(50" C. 



Several of these cotton swabs may be prepared at once and kept on hand. The 

 swab, carefully removed and saturated with the material to be examined, is at once re- 

 turned to the tube ; this is plugged, and may be thus safely transported. l 



II. Yeasts. 



These micro-organisms larger than bacteria and mostly saprophytes 

 consist of oval or spheroidal cells with granular protoplasm and a thin 

 membrane. They multiply by sprouts or buds from 

 the parent cell (Fig. 84). The new individuals may 

 separate from the old, or may cling to them so that 

 chain-like combinations may occur. They sometimes 

 form endogenous spores, known as ascospores. Some 

 FIG 84 -YEAST-SEC 8 P ecies develop bright colors in their growth. 



charomyces. There are many forms of yeasts which are concerned 



in various phases of fermentation. Some of these,' al- 

 coholic fermentation for example, are of great economic importance." 

 Certain forms of yeasts nourish in the stomach during digestive disorders 

 and in the bladder in diabetes, without the incitement of lesions. Sev- 

 eral forms of yeast have been proven to be pathogenic in lower animals 

 and in man. In 1894 Gilchrist 3 reported a case of blastomycetic derma- 

 titis in man. Since that time other cases have been observed. 4 



III. Moulds. 



The moulds are considerably more complex in structure than either 

 the bacteria or the yeasts. Some of the forms are very common and uni- 

 versally known. In general, it may be said that the moulds consist of 

 a series of delicate, translucent, branching jointed threads mycelium 

 usually giving rise to hyphce from which, either directly or in more com- 

 plex form through the intervention of a special structure, the sporangium, 

 the spores are developed (Fig. 85). The moulds which are apt to occur 

 in the human body may be of the former more simple, or of the latter, 

 more complex type. 5 Among the simpler forms of moulds which occur 

 in the body may be mentioned the Achorion Schonleiuii, Microsporon 



1 For further suggestions for the collection and examination of specimens for micro- 

 organisms, and for references to studies on the bacteria of the human body, see p. 260. 



2 For a consideration of the relationship of micro organisms to various forms of fer- 

 mentation, with bibliography, consult Jorgemon, "Micro-organisms and Fermentation," 

 Eng. translation, 1900. 



3 Gilchrist, Johns Hopkins' Hospital Reports, vol. i., p. 269. 



4 For a resume of the subject of pathogenic blastomycetes with experiments and 

 bibliography, see Foulerton, Journal of Pathology and Bacteriology, vol. vi., p. 37, 

 1900; and Sternberg, Ziegl. Beitr., Bd. xxxii., 1902, p. 1; also Rtcketts, " Blastomycosis 

 of Skin," Jour. Med. Res., vol. vi., 1901, p. 377; also Otis and Scans, Jour. Am. Med. 

 Assn., October 31st, 1903. 



5 See Efnon, "fitude sur 1'aspergillose chez les animaux et chez 1'homme," Paris, 

 1897; also Leopold and Levi, Gaz. cles Hopitaux, June 26th, 1897, Bibl.; also Pierson 

 and Kai-enel, University Med. Mag., August, 1900; also Sayer, " Pueumonomykosis 

 aspergillina," Jena, 1900. 



