GROWTH OF MASSIVE CULTURES OF BACTERIA 35 



operation, and with a crop every three weeks, one may 

 obtain several kilograms within a few months. 



Three successive crops of the colon bacillus have been 

 grown on the same agar, resterilizing and reinoculating 

 after each harvest, but the third crop is not abundant. It 

 has been found to be well to follow the example of the 

 scientific agriculturalist and rotate the crops. Colon 

 grows well after typhoid, but typhoid does not grow well 

 after colon. Five crops have been obtained in the following 

 order: (1) pneumococcus, (2) typhoid, and (3) three suc- 

 cessive colon growths, or better, non-pathogenic bacteria 

 following one colon growth. 



Many non-pathogenic organisms, the colon, typhoid, 

 pneumococcus, and diphtheria organisms, have been grown 

 on the tanks, and so simple is this method of obtaining 

 bacterial cellular substance in large amount that any intel- 

 ligent person, after some experience, may repeatedly go 

 through the whole manipulation, producing growth after 

 growth, without contamination. In the laboratory it is 

 best to have one man make a specialty of producing these 

 growths. 



The anthrax and tuberculosis cellular substances with 

 wliich we have worked have not been produced in the 

 tanks. The former has been grown in Roux flasks and the 

 latter in glycerin beef- tea cultures. After these growths 

 have been obtained, their further preparation has been the 

 same as that already outlined. 



Prepared, as described, the bacterial cellular substances 

 form fine, white, or yellowish-white powders. This is true 

 even of the chromogenic bacteria, such as b. violaceus and 

 b. prodigiosus, the pigment being removed from the cells 

 by its solubility in alcohol. One of our former students, 

 Detweiler, 1 studied some of these pigments, but these do 

 not concern us at present, because they constitute no part 

 of the cellular protein. The same is true of the other bodies 

 soluble in alcohol and ether. The extracts made with these 



1 Trans. Assoc. Amer. Phys., 1902, xvii, 246. 



