188 MEDICAL MYCOLOGY 



character for the separation of species. The power to ferment other sugars is 

 so variable (in their opinion) that it should not be used to separate species. 



A study of utilization of carbon sources is helpful, using Raulin's neutral 

 solution, replacing the sucrose successively by glucose, maltose, lactose, man- 

 nose, fi-uctose, inulin, starch and soluble dextrin, methyl alcohol, ethyl alcohol, 

 glycerol, formic acid, acetic acid, oxalic acid, tartaric acid, and citric acid. In 

 the case of the above-mentioned acids, the tartaric acid is replaced by the 

 acid in question rather than the sucrose. Similarly sources of nitrogen are 

 studied, substituting 1% potassium nitrate, potassium nitrite, ammonium car- 

 bonate, urea, glycine, asparagine, and White's [Witte?] peptone for the nitro- 

 gen source of the Raulin's neutral solution. Initial and ultimate hydrogen ion 

 concentration should be recorded in these tests. In the liquid media, these 

 authors suggest cultivation in graduated centrifuge tubes. After notes on the 

 character of growth are taken, these tubes are centrifuged for 5 minutes at 

 2,000 revolutions per minute and the quantity of fungous cells at the bottom 

 is taken as an approximate indication of the amount of growth. In the case 

 of the sugars it is usually better to sterilize separately and add to the sterile 

 Raulin's solution to avoid possible hydrolysis from the hydrogen ions of this 

 solution. For the effect of different sugars on the morphology, see the inter- 

 esting case of Blast odendrion intermedium (Fig. 38). 



Production of hydrogen sulphide (Kliger's method), hydrolysis of starch 

 (Committee method), indol production (Ehrlich method modified by Gore) 

 may also be tried, but so far have not yielded much information useful in 

 classification. 



Finally parasitism and pathogenicity should be studied on experimental 

 animals. 



Needless to say, this elaborate and ideal method has not been carried out 

 for most organisms so far described in this group. It is often impossible 

 to identify recently studied strains with older species in the literature, owing 

 to the total lack of characters used by one author in the description by an- 

 other. This is especially notable in the case of Castellani, who early aban- 

 doned any mention of morphology and relied wholly on fermentation and 

 enzyme reactions. The validity of fermentation reactions has been much dis- 

 cussed in recent years (for general criticisms see pp. 63, 64), often without much 

 apparent realization of the meaning of results or the limitations of the meth- 

 ods employed (e.g., Castellani 1933). Under Castellani 's influence, very little 

 attention has been paid to morphology until very recently, although we have 

 occasional attempts to correlate morphology and fermentation reactions ; e.g., 

 Fineman (1921) Nye, Zerfas & Cornwell (1928), Mackie & Chitre (1928). Re- 

 cently the pendulum seems to be swinging the other direction, and we have 

 Milochevitch (1929), Talice (1930), Shaw (1931), and Langeron & Talice 

 (1932) emphasizing morphology very strongly, and searching for media which 

 will produce normal mycelium rather than sprout mycelium, and in the case 

 of myself and my students (Rewbridge, Dodge & Ayres 1929, Moore 1933- 

 1935 and much unpublished data) rather successful search for sexual or per- 



