770 EXPEEIMENT STATION EECORD. 



The second study deals with the metabolism of certain rapidly-growing human 

 tubercle bacilli in broth free from lipoids and fatty substances. " In order to 

 determine what part, if any, these lipoidal substances in the amounts in which 

 they occur in ordinary media might play in the metabolism of tubercle bacilli, 

 media were made up from ingredients in which these substances were definitely 

 and quantitatively eliminated. ... In glycerin broth, after a slight initial 

 increase in ammonia amounting to about 2 per cent of the total nitrogen of the 

 medium, the ammonia appears to decrease in amount, so that at the end of the 

 experiments it is less than that contained in the uninoculated media. At the 

 end of the second week the glycerin broth cultures of both strains of the 

 tubercle bacillus were found to be slightly viscid, and by the end of the fourth 

 week this viscosity was very marked. The reaction of the medium to phe- 

 nolphthalein becomes progressively alkaline in spite of this decrease in am- 

 monia. ... It is conceivable that at least some of this ammonia is tied up 

 in the bodies of the bacteria, and inasmuch as the organisms studied in this 

 connection form firm tenacious pellicles, leaving the medium beneath them per- 

 fectly clear and free from bacteria, it was a comparatively simple matter to make 

 a determination of the total nitrogen of the clear underlying broth. . . . 

 The results show that a very considerable proportion of the total nitrogen in the 

 medium is, apparently, tied up in the bodies of the bacteria. . . . While 

 these experiments do not by any means prove that the substance or substances 

 conferring acid-fastness on these organisms are derived from protein deriva- 

 tives alone, yet it would seem that an experiment of this sort carried out under 

 similar conditions, with especial emphasis on the fat and wax content of the 

 organisms, would throw some definite light on the physiology of the formation 

 of fats and waxes from protein." 



The purpose of the study on the metabolism of the bacilli in a modified 

 Uschinsky medium was to determine the cause of the recession of ammonia by 

 the old cultures of avirulent tubercle bacilli employed in the second study with 

 media of very simple composition. " For the purpose of this investigation a 

 medium was made consisting of 4 gm. of aspai'agin, 2 gm. of disodium hydrogen 

 phosphate, and 5 gm. of NaCl to the liter of distilled water as a basis. This 

 medium was divided into three parts, to one of which was added 1 per cent of 

 dextrose, to a second 1 per cent of mannit, and to a third 3 per cent of glycerin, 

 as additional sources of carbon. They were then sterilized under parallel condi- 

 tions in 100 cc. amounts. . . . An attempt was made to grow the organisms 

 in the asparagin solution without any additional source of carbon, but this was 

 unsuccessful. . . . The determinations were made in duplicate at weekly 

 intervals for six weeks, and, with the exception of glycerin, the same recession 

 of ammonia appears as was noted in the previous experiments. The glycerin 

 does not show this recession. The extent of the recession was somewhat less 

 marked than in peptone-containing media, but the growth, it should be noted 

 parenthetically, was much less luxuriant. . . . Inasmuch as these organisms 

 undoubtedly derive their nitrogen from the nitrogen of the asparagin, it might 

 be assumed that the acid formed was due to the removal of the basic group of 

 the asparagin. There is a certain amount of evidence in favor of this supposi- 

 tion, for the organism in question would not develop in this asparagin solution 

 without an additional source of carbon. ... At the same time the break- 

 down of asparagin, as measured by the increase in ammonia, was so great that 

 it would be unjustifiable to assert that these substances exert a sparing action 

 for the nitrogen. The extent of the breakdown of asparagin was, roughly, the 

 same in each of these media. Although the maximum degree of nitrogen 

 metabolism was apparently not reached even at the end of six weeks in the 

 glycerin medium, at the end of four weeks, generally speaking, the maximum 



