FIFTH LECTURE. 



YEAST PLANT. 



For comparison, let us turn again to the yeast plant. Here 

 we have no blood streams to interfere with our study of phe- 

 nomena. The same cells that emit the soluble ferment which 

 performs the primary digestion, appropriate the results of that 

 digestion, not individually, but en masse. That is, each cell 

 individually excretes, so to speak, the material, the soluble 

 ferment, that performs primary digestion. This digestion is 

 performed by the whole amount of material excreted, inde- 

 pendently of the individual cell, but in the appropriation of 

 the results of this primary digestion, each individual cell acts 

 for itself only, and independently of all other cells. The 

 result is the building up of the tissue of the cells by remolecu- 

 lizing the original elements into new forms, with the elimi- 

 nation of waste products. 



In this case the waste products are alcohol and carbonic 

 acid. One is the same as in the animal, carbonic acid, the 

 other is different. These waste products agree, in their eifects 

 upon the activity of the plant, with the waste products of the 

 animal upon its life force. Alcohol, in a certain quantity, 

 stops the growth, the activity, of the yeast plant which pro- 

 duced it, and if sufficiently concentrated, destroys it. Urea 

 does the same for animal life. 



These excretory products differ widely among the lower 

 forms of life, and yet, as we shall show in another lecture, re- 

 tain a constant resemblance. 



In case of the mycodermi aceti, the acetic acid plant, the 

 excretory products are carbonic acid and acetic acid. With 



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