G ELEMENTARY BIOLOGY. [l. 



sugar. A small part breaks up into Glycerine and Succinic 

 acid, and one or two per cent, is not yet accounted for, but is 

 perhaps assimilated by the Torulce. 



This is the more probable as Torulce will grow and multiply 

 actively in a solution in which sugar and Ammonium Nitrate 

 replace the Ammonium Tartrate of the former solution, in 

 which case the carbon of the Protein, Cellulose and Fat manu- 

 factured, must be obtained from the sugar. Moreover, though 

 oxygen is essential to the life of the Torulct, it can live in 

 saccharine solutions which contain no free oxygen, appearing, 

 under these circumstances, to get its oxygen from the sugar. 



It has further been ascertained that Torulce flourish 

 remarkably in solutions in which sugar and pepsin replace 

 the Ammonium Tartrate. In this case, the nitrogen of their 

 protein compounds must be derived from the pepsin ; and 

 it would seem that the mode of nutrition of such Torulce 

 approaches that of animals. 



LABORATORY WORK. 



Sow some fresh baker's yeast in Pasteur's fluid 1 with 

 sugar and keep it in a warm place : as soon as the mixture 

 begins to froth up, and the yeast is manifestly increasing in 

 quantity, it is ready for examination. 



1 Pasteur's fluid : 



Potassium Phosph 2 parts. 



Calcium Phosph i 



Magnesium Sulphate 2 



Ammonium Tartrate 100 



[Cane sugar 1500 ,] 



Water 8576 



10,000 parts. 



The sugar is to be omitted when Pasteur's fluid "without sugar" is 

 ordered. Pasteur himself used actual yeast ash; the above constituents give 

 an imitation ash, which, with the ammonium salt and sugar, answers all 

 practical purposes. 



