1 22 THE GERM THEORY OF DISEASE. 



labors of Pasteur have thrown much light upon this subject. 

 The fact that the acetic acid plant will again remoleculize the 

 waste product of the vinous yeast plant, alcohol, and after 

 that the mucidines will still remoleculize the acetic acid, con- 

 verting it, in turn, into other compounds, is full of instruction 

 for all these processes. Why is it that the yeast plant cannot 

 grow continuously in the same menstruum, if proper food 

 material be furnished it? It is a well known fact that only 

 a certain percentage of alcohol can be formed in this way, 

 and that to obtain a greater percentage we must resort to 

 distillation. The plant is choked by its own excreta, alcohol. 

 If this could be eliminated the growth of the plant could be 

 continued. 



An example of this is found in the bacterium lactis. If 

 lime is added to the solution, lactate of lime is formed and 

 the excretory product of the plant, lactic acid, is artificially 

 eliminated, and the plant is found to grow continuously in 

 the same menstruum, as long as supplied with food material, 

 and lime to fix or eliminate its excreta. The form of excre- 

 tion employed by the higher plants is artificially produced. 

 This law of the relation of excretory products to the life that 

 formed them is universal. It applies with the same force to 

 the micro-organisms that it does to the higher animals, or to 

 man himself. 



It would seem that the vegetable world is divided into two 

 great classes of life forms, and that ifc is the office of the one 

 to build up, and the office of the other to tear down. Of all 

 the life forms, the higher plants have the greatest power of 

 structure building, both as regards quantity, in comparison 

 with the amount of the material consumed, and as to the 

 actual quantity of structure formed ; while, in the lower 

 plants, the bacteria and their allied forms, exactly the opposite 

 of this is found, in every particular. No other form of life 



