CHAPTER XL 



METHODS OF PURE CULTURE. 



82. Nutrient Solutions. 



IN 15 of the Introduction it was stated that Liebig's theory regarded the 

 disintegration of the albuminoids as the true active agency in fermentation. 

 PASTEUR (VII.), the active opponent of this theory, interested himself in the 

 preparation of artificial media which, though free from albuminoids, began to 

 ferment when inoculated with a minute quantity of fermentative organisms 

 (e.g. a trace of yeast). The oldest of these, generally known as Pasteur's fluid, 

 consists of 



Grams. 



Water 100.0 



Ammonium tartrate i.o 



Cane-sugar 10.0 



Yeast-ash (corresponding to one grin, yeast) . . . 0.075 



and was intended preferably for the cultivation of the higher fungi (yeast in 

 particular). Its suitability for bacterial cultures was examined by Colin, who 

 found that for this purpose the sugar could be dispensed with. On the basis of 

 researches into the requirements of yeast as regards mineral matters, ADOLF 

 MAYER (I.) proposed to employ, in place of the yeast-ash, which is soluble only 

 with difficulty, an artificially prepared solution of the salts of which this ash is 

 known from experience to consist. Utilising this report, COHN (I.) prepared a 

 nutrient solution which he named " normal bacterial liquid," and which was 

 composed of 



Grams. 

 Water joo.o 



Potassium acid phosphate (KH 2 P0 4 ) 

 Tribasic calcium phosphate (Ca3(P0 4 ) 2 ) 

 Crystallised magnesium sulphate . 



Ammonium tartrate 



0-5 



0.05 



0.5 



i.o 



NAGELI (IV.), relying on the results of his researches (indicated in chapter ii.) 

 on bodies suitable for the nutrition of the lower fungi, prepared three " normal 

 liquids for fission fungi," one of them having the subjoined constitution : 



Grams. 



Water 100.0 



Di-potassium phosphate (K 2 HP0 4 ) . . . . . o. i 



Crystallised magnesium sulphate 0.02 



Calcium chloride o.ot 



Ammonium tartrate i.oo 



The nutrient solutions hitherto described play a great part in earlier myco- 

 logical literature, on which account their constitution is now given, though at 

 present they are but seldom used. 



On the other hand, a second nutrient solution given by Pasteur, viz., yeast- 

 water, is still frequently used. To prepare this solution, about 100 grms. of 

 thick brewer's barm (or 75 grms. of pressed yeast) are placed in a tin can with 



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