iv.] YEAST. 85 



tissues of animals and plants " Les organes e'le'men- 

 taires de leurs tissus, comparables aux petits vege'taux 

 des levures ordinaires, sont aussi les ddcompositeurs des 

 substances qui les environnent." 



Almost at the same time, and, probably, equally guided 

 by his study of yeast, Schwann was engaged in those re- 

 markable investigations into the form and development 

 of the ultimate structural elements of the tissues of 

 animals, which led him to recognize their fundamental 

 identity with the ultimate structural elements of vege- 

 table organisms. 



The yeast plant is a mere sac, or " cell," containing a 

 semi-fluid matter, and Schwann's microscopic analysis 

 resolved all living organisms, in the long run, into an 

 aggregation of such sacs or cells, variously modified ; and 

 tended to show, that all, whatever their ultimate compli- 

 cation, begin their existence in the condition of such 

 simple cells. 



In his famous " Mikroskopische Untersuchungen " 

 Schwann speaks of Torula as a " cell ; " and, in a re- 

 markable note to the passage in which he refers to the 

 yeast plant, Schwann says : 



" I have been unable to avoid mentioning fermentation^ because it is 

 the most fully and exactly known operation of cells, and represents, 

 in the simplest fashion, the process which is repeated by every cell of 

 .the living body." 



In other words, Schwann conceives that every cell of 

 the living body exerts an influence on the matter which 

 surrounds and permeates it, analogous to that which a 

 Torula exerts on the saccharine solution by which it is 

 bathed. A wonderfully suggestive thought, opening up 

 views of the nature of the chemical processes of the 

 living body, which have hardly yet received all the 

 development of which they are capable. 



Kant defined the special peculiarity of the living body 



