18 HARRY WARREN ANDERSON 



bacteriologist makes use of these properties. Will ('03-'15) has made an 

 exhaustive study of the asporogenic yeasts, using biochemical properties and 

 cultural characters as a means of differentiating the 'forms' obtained. Geiger 

 ('10) also uses Will's methods in his study of the species of the genus Pseudo- 

 monilia. The assimilation of different sugars, alcohols and organic acids, the 

 production of alcohol and acids, the resistance to alcohol, etc., are some of the 

 characters determined for each form studied. Both authors also emphasize the 

 importance of the use of 'giant colonies.' 



Lutz and Gueguen ('01) have proposed a classification based on morphologic 

 and cultural characters. They wish to establish a standard method of proce- 

 dure to use with all hyphomycetes such as the bacteriologists employ for dif- 

 ferentiating bacterial species. They recommend the employment of a synthetic 

 medium (Raulin's solution*) with and without various sugars, the addition of 

 other carbohydrates, glycerin, etc. They also employ milk, potato, and carrot 

 slants and egg albumin. 



The complicated procedure recommended by Will cannot be undertaken in 

 ordinary routine work on account of the complex chemical analysis employed, 

 and the time necessary to complete the study of a species. This is especially 

 true where pathogenic yeasts are to be studied, since the method employed by 

 Will requires at least 3 months for complete observation. The procedure 

 recommended by Lutz and Gueguen has much in its favor, but does not include 

 several of the most important differentiating mediums. The yeast water 

 employed by Will and others is more satisfactory as a basic solution although 

 its chemical composition is not as definite as that of the synthetic medium of 

 Raulin. 



Variations in cultural and physiologic characters are encountered in the 

 yeasts, even to a greater extent than in the bacteria. This is especially true 

 in streak cultures on solid mediums such as agars, carrot and potato slants. 

 Variation in fermentation of sugars and in acid-production is also frequently 

 encountered. Ashford ('15d) has recorded the fermentation of galactose and 

 sucrose by his sprue organism at one time, while at another time it failed to 

 produce gas in these sugars. 



In studying the organisms isolated a large number of different mediums 

 were used and the cultural, physiologic, and biochemical properties of these 

 yeasts were studied under a wide range of conditions. The object has been 

 to secure differential methods which are based on procedure ordinarily employed 

 in bacteriologic or mycologic laboratories. At the same time it is realized that 

 additional information along biochemical lines aids in a surer differentiation 

 and gives more insight into the complicated life processes of the organisms 

 concerned. The mediums which have been found most useful are discussed 

 in detail in the next section. 



Agglutination and precipitation tests were not attempted. There- is a pos- 

 sibility that some satisfactory basis for specific differentiation may be obtained 

 by the use of these properties, though the results obtained by various investi- 

 gators thus far have been disappointing. 



* Raulin's solution: 



Distilled water 1,500 gm. 



Sucrose 70 gm. 



Neutral potassium tartrate 6.5 gm. 



Ammonium nitrate 4.5 gm. 



Potassium phosphate -6 gm. 



Magnesium carbonate -4 gm. 



Potassium sulphate -25 gm. 



Ferric sulphate .07 gm. 



Zinc sulphate -07 gm. 



Potassium silicate '07 gm. 



