SCIENCE. 



[N. S. Vol. V. No. 130. 



bacillus which have undergone functional 

 derangement as a consequence of their en- 

 vironment. A short resume of our experi- 

 mental work is given in this paper, but we 

 fear that it is insufficient in regard to the 

 details of experiments and the results ob- 

 tained to maintain our conclusions. 



From the observations and deductions of 

 several competent investigators, the patho- 

 genesis of the colon bacillus is due to culti- 

 vation in the living fluids of the animal 

 bodjr, which are supplied with an unusual 

 amount of proteid substance by the process 

 of inflammation. We have made experi- 

 ments with the members of the colon group 

 to ascertain to what extent the proteolytic 

 activity can be increased by growth upon an 

 artificial medium containing large amounts 

 of proteid material. The medium used for 

 our experiment was a bouillon free from 

 sugar and containing a large per cent, of 

 fresh peptones derived from beef muscle by 

 the action of trypsin. These peptones, ac- 

 cording to Pere, are capable of forming 

 more indol than those produced by the 

 action of pepsin or any other enzyme. 



Series of cultures compi-ising, severalljr, 

 the typical colon bacillus, transitional forms 

 of the colon group, and the typical typhoid 

 bacillus, have been carried through a series 

 of cultures in this medium, each culture be- 

 ing changed to fresh media every seventy- 

 two hours, and the old culture tested for 

 indol for the purpose of obtaining an approx- 

 imate estimation of the proteid digestion. 



The result of these experiments was that 

 under these conditions the proteolj'tic func- 

 tion is increased in activity, so that cultures 

 of the typical colon bacillus gave, in the 

 second generation, after growth for three 

 days in 25 c. cm. of the medium, an indol reac- 

 tion of a blood-red color in some instances, 

 and requiring in every culture from 10 to 

 15 c. cm. of a 0.1 per cent, indol solution to 

 give the same depth of color to 25 c. cm. of the 

 sterile medium. Transitional forms of the 



colon group which have hitherto been sup- 

 posed to be devoid of the indol-producing 

 power, after cultivation for three or four 

 generations in this medium gave a marked 

 indol reaction. Seventeen different speci- 

 mens of the typhoid bacillus, obtained by 

 us from some of the best known laboratories 

 in this country, gave also a marked indol 

 reaction after passing through a series of 

 changes in this medium. 



Hesult of excess of one function. The re- 

 sult of the excessive discharge of one func- 

 tion, viz., proteolysis, which has been pro- 

 duced by growth in the fresh peptone 

 bouillon free from sugar, is, first, an increase 

 of the proteolytic activity as shown by the 

 increased amount of indol produced in typi- 

 cal colon cultures, and the production of 

 indol by organisms supposed to be devoid 

 of this property: viz., atypical forms of the 

 colon bacillus, and the typical typhoid ba- 

 cillus; secondly, after the maximum of indol 

 production is reached, a decrease in proteo- 

 lytic activity occurs, shown by the lessened 

 amount of indol, and, finally, after several 

 generations, the attenuation and premature 

 death of the organism takes place. 



Indol production as an index of pathogenesis. 

 An experiment relating to this question has 

 been carried on for over a year with a viru- 

 lent culture of the colon bacillus. The cul- 

 ture was tested for indol and virulence as 

 soon as it was isolated. The indol reaction 

 was very marked, and 0.5 c. cm. of a bouillon 

 culture proved invariably fatal to guinea 

 pigs of 500 grammes weight. It was then 

 kept for five months on agar-agar with but 

 few changes, when it was again tested. A 

 faint indol reaction was obtained, and 1 to 

 2 c. cm. of a bouillon culture was required to 

 kill an animal of 300 to 500 grammes weight. 

 This culture was then placed in the alkali- 

 peptone solution and changed to fresh me- 

 dium twice in seven days, when tests were 

 again made. The color of the indol reac- 

 tion was very intense, and 0.3 c. cm. of an 



