38 BACTEBIOLOOY. 



of whose intimate chemical nature little or nothing is 

 known; toxalbumins being those that partake of the 

 chemical nature of albumins ; ^vhile ptomains are crys- 

 tallizable products of bacterial activity which, physically 

 speaking, are analogous to the ordinary vegetable alka- 

 loids. 



"We have said that through the agency of chlorophyll, 

 in the presence of sunlight, the green plants are enabled 

 to obtain the amount of nitrogen and carbon which is 

 necessary to their growth from such simple bodies as 

 carbon dioxide and ammonia, which they decompose 

 into their elementary constituents. The bacteria, on 

 the other hand, owing to the absence of chlorophyll 

 from their tissues, do not possess this power. They 

 must, therefore, have their carbon and nitrogen pre- 

 sented as such, in the form of decomposable organic 

 substances. 



In general, bacteria obtain their nitrogen most 

 readily from soluble albumins, and to a certain extent, 

 but by no means so easily, from salts of ammonium. In 

 some of Nageli's experiments it appeared probable that 

 they could obtain the necessary amount of nitrogen 

 from inorganic nitrates. At all events, he was able 

 in certain cases to demonstrate a reduction of nitric to 

 nitrous acid and ultimately to ammonia. Neverthe- 

 less, in all of these experiments circumstances point to 

 the probability that the nitrogen obtained by the bac- 

 teria for building up their tissues in the course of 

 their development was derived from some source 

 other than the nitric acid or the nitrates, and that the 

 reduction of this acid was most probably a secondary 

 phenomenon, It must be borne in mind, however, that 



