H. (jr. Thornton 



259 



of the medium on the rate of multiplication of B. dendroides, comparing 

 its growth on media containing, respectively, peptone, "lemco, " and 

 a pure amino-acid. 



The medium used as a basis had the following composition : 



Medium CV. 



1 gm. FeCls 



0-2 „ KNO3 



0-1 „ Mannitol 



0-1 „ Water 



To the above medium the organic nitrogen supply was added in an 



amount giving nitrogen approximately equivalent to 0-05 per cent. 



K2HPO4 

 MgS04.7H20 



CaClg ... 

 NaCl ... 



0-002 gm. 

 0-5 „ 

 1-0 „ 

 1000 c.c. 



36 



48 



12 24 



Hours growth. 



Fig. 6. B. dendroidea. Effect of the organic nitrogen source on multiplication. 



asparagine. The reaction of the media was standardised to _/)H 7-4, 

 immediately prior to autoclaving. Duplicate tubes containing 10 c.c. 

 of medium were inoculated with 0-5 c.c. of a suspension of a young agar 

 culture of B. dendroides. The tubes were incubated at 30° C, and, at 

 intervals of 12 hours, the number of organisms per c.c. was estimated 

 from counts made in a Thoma counting chamber, the mean count of 

 the duplicate tubes being taken in each case. 



The curves, Fig. 6, show the multiplication of the organisms in media 

 containing "lemco," peptone, and asparagine. 



It will be seen that, with asparagine, the multiplication is very 

 markedly less rapid than in the presence of peptone or meat extract. 



17—2 



