16 PHYSIOLOGY OF BACTERIA 



In another place, Rubner mentions that yeast in sugar 

 solution lost 58% of its nitrogen, while the same yeast 

 without sugar lost 89%. 



(c) CHEMICAL CONCEPTION OF "WEAR AND TEAR" 



The constant excretion of nitrogenous products by 

 the starving organism has been explained as the result of 

 the continuous '^wear and tear" of the cells. It seems 

 that most physiologists consider this to be a mechanical 

 wearing of the organism, and what originally was to be 

 just a simile is now considered the true explanation. 

 The books of Bayliss and of Cathcart give no other. 



Yet, this interpretation seems rather unsatisfactory. 

 A mechanical wearing of a resting man or animal during 

 a starvation experiment is difficult to conceive. Many 

 experiments have shown that mechanical labor, unless 

 it is overdone, does not increase, to any marked degree, 

 the wear and tear, as measured by the nitrogenous 

 excretions. This is quite contradictory to any mechani- 

 cal conception of the wear and tear (Bayliss p. 267, 

 Cathcart p. 133). 



Euler (Euler-Lindner, 1915) offers a biochemical theory 

 already quoted on p. 10. It is essentially the same as 

 that of Rahn (1915) who explains endogenous catabolism 

 as the result of the instability of living protoplasm or 

 parts of it. All cells contain enzymes. All enzymes are 

 unstable and deteriorate with time. 



While it is generally admitted that enzymes in solution 

 cannot be kept permanently active, it is often stated that 

 they do not undergo deterioration inside of the cell. 

 The only evidence to substantiate this claim is the fairly 

 constant enzyme content of the cell. This proof is not 

 conclusive since we know that all cells can produce the 

 enzymes which are found in them. 



