Studies in Fat Metabolism of Timothy Grass Bacillus. 269 



rapidly than the " phosphatide " fraction, until an equilibrium is established 

 in which the "phosphatide" fraction is maintained at the higher value. 

 This suggests that the " fat " fraction represents a form of stored food 

 material which is drawn upon when external sources "of carbonaceous food 

 material fail, whilst the " phosphatide " fraction, winch decreases less rapidly, 

 is probably partially composed of some unit essential to the chemical struc- 

 ture of the cell. The duplicate determinations of the "fat" fraction on the 

 twenty-eighth day show a wide variation. This is in the period of rapid 

 utilisation of stored fat. A slight retardation of the point at which maximum 

 growth was attained and utilisation of fat began would result in a large 

 observable difference at this point. 



The results of starvation thus show that the fat metabolism of the higher 

 animals has its prototype in this micro-organism. 



It also appears from the curve that the protein nitrogen decreases very 

 slightly during the first fourteen days of starvation, the drop between the 

 twenty-eighth and thirty-sixth day being actually within the experimental 

 error. The bacillus thus seems to preserve its protein material intact. It 

 must be remembered, however, that throughout the experiment ammonia 

 was present in the medium ; the bacillus may therefore have broken down 

 cell protein as well as lipoid material, and have reconstituted the former 

 from the ammonia of the medium and the fatty acid chains of the lipoids. 

 Unfortunately no material was available for a final protein nitrogen estimation 

 on the sixtieth day. 



It will be noticed that there is a small but definite growth of bacillus 

 on the seventh day of the experiment, while the glucose is apparently 

 untouched. "We have confirmed this observation repeatedly in experiments 

 where glucose forms the only organic food material. It may have its ex- 

 planation in the small amount of food material carried over from the potato 

 slopes, or it may be that in the initial breakdown of the sugar molecule a 

 small quantity of a reducing body accumulates which is erroneously 

 estimated as glucose ; such a body has been searched for but not as yet 

 found. 



During the course of the foregoing experiment, in 100 c.c. of medium, ap- 

 proximately 1 grm. of glucose and 1 grm. of acetic acid (as acetate) dis- 

 appeared, together with certain unascertained quantities of mineral material 

 and ammonia. Their place was taken by - 018 grm. of protein nitrogen, 

 corresponding roughly to O'l grm. protein, and 041 grm. of mixed lipoid 

 material. 



In a similar experiment in which glucose was the sole organic constituent 

 of the medium, 1 grm. of glucose gave rise to 0'0189 grm. of protein nitrogen 



