FIELD STUDIES OF THE DISEASE, 53 



regions where the disease does not occur.^ As there is no complete 

 evidence for or against tliis, the question must for the present remain 

 unsettled. An explanation might, however, be sought in consid- 

 ering what passes for Bacillus coli as a group of organisms, the mem- 

 bers of which, while alike in the usual cultural characters, possess 

 var3nng pathogenic properties.^ The only other possible explana- 

 tion is a difference in the soil or climate. The necessary evidence to 

 support such a theory is, however, entirely lacking. 



'An earwig similar to or identical with the Cuban species has been found by the writer in Porto 

 Rico, but the turkey buzzard is either entirely absent or at least rare on that island. 



2 Since this statement was written Daniel D. Jackson has published a very instructive paper (Journal of 

 Infectious Diseases, March, 1911, pp. 241-249) in which he maintains Bacillus coli to be a group of related 

 species, divided by him as follows: B. cummunior (Durham), B. communis (Escherich), B. acrogenes 

 (Escherich), B. acidi-lactici (Hueppe). The first two species are separated from the second two by their 

 gas production with dulcit and the first of each of these two groups may be separated from the second by 

 its gas production with saccharose. 



Each of these species may be separated into four possible varieties in accordance with their gas produc- 

 tion with mannit and raflinose. Tliree varieties each of the first and fourtli species are now known, two 

 varieties of the third, and all four possible varieties of the second group have been found. 



In a diagram 21 varieties of Bacillus coli are given, four of which are as yet unknown. 



Bacillus communioT (Durham). — Variety Ai: Fermentation with gas production with dextrose, lactose, 

 dulcit, saccharose, mannit, and raffuiose; milk coagulated, nitrate reduced, motile, and indol positive. 

 Variety A2: Fermentation the same as Ai; motile, reduces nitrate; differs from Ai in not producing indol. 

 Variety B: Ferments with gas production with dextrose, lactose, dulcit, saccharose, and mannit, but 

 forms no gas with raffinose. Also distinguished by no coagulation in milk even after heating and by slow 

 formation of gas in dulcit. This latter test usually takes three days for the gas formation to become active. 

 Motile, indol positive, nitrate reduced. Variety C: Fermentation with gas production with dextrose, 

 lactose, dulcit, saccharose, and raffinose; forms no gas with mannit; milk coagulated, nitrate reduced, motile, 

 and indol positive. 



Bacillus communis (Escherich). — Variety A: Fermentation with gas production with dextrose, lactose, 

 dulcit, mannit, and raffinose; no gas formation with saccharose; motile, indol slight, nitrate reduced. 

 Variety B: Fermentation with gas production with dextrose, lactose, dulcit, and mannit; no gas produc- 

 tion with saccharose and raffinose; milk coagulated, nitrate reduced, motile, and indol positive. This 

 appears to be the most common variety of B. communis. Variety C: Fermentation with gas production 

 with dextrose, lactose, dulcit, and raffinose; no gas production with saccharose or mannit; nitrate reduced, 

 indol positive, motile. Variety D: Fermentation with gas production with dextrose, lactose, and dulcit; 

 no gas production with saccharose, mannit, or raffinose; nitrate reduced, indol positive. 



Bacillus aerogenes (Escherich).— Variety Ai: Fermentation with production of gas with dextrose, lactose 

 saccharose, mannit, and raffinose; no gas production with dulcit; indol positive, nitrate reduced, motility 

 negative; viscous growth on agar and in lactose bile; in the latter it can be drawn out into a long, thin string. 

 Variety As: Fermentations the same as Ai; motile, indol negative, nitrate reduction positive; differs 

 from Ai in being less viscid or stringy when touched with the needle; in being motile, and indol negative. 

 Variety A3: Fermentations and all tests with one exception same as Aj; liquefies after 26 days; differs 

 from As in being slightly liquefying in gelatin stab after about 26 days. The total gas and percentage of 

 CO2 is high when grown in dextrose brotli and particularly in liver broth. This species has been at times 

 grouped with B. cloacae (Jordan), l>ut the former never fails to produce gas with lactose, while typical 

 B. cloacae apparently always gives negative results, when dextrose-free lactose solutions are used. Another 

 marked distinction is that true B. cloacae after rejuvenating is always strongly liquefying, while B. aero- 

 genes A3 never liquefies before 20 days, even after careful rejuvenation over long periods. Variety Bi: 

 Forms gas with dextrose, lactose, saccharose, and mannit, but no gas with dulcit and raflBnose; nonmotUe, 

 indol negative, nitrate reduced; viscous growth on agar and in lactose bUe. May be dra^\•n out into a thin 

 string by using a platinum needle. Variety Bs: Differs from Bi in being motile, indol positive, and non- 

 viscous in lactose bUe. 



Bacillus acidi-lactici (Hueppe).— Variety Ai: Fermentation with gas production with dextrose, lactose, 

 mannit, and raffinose; no gas production with dulcit and saccharose; nonmotile, indol positive, nitrate 

 reduction positive. Variety As: Fermentation same as Ai; indol positive, nitrate reduction positive; 

 differs from Ai in being motile. Variety B: Fermentation with gas production with dextrose, lactose, 

 and mannit; no gas production with dulcit, saccharose, or raffinose; milk coagulated, nitrate reduced, 

 motile, and indol positive. Isolated by Melia in nine strains from human feces. Often exceeding in 

 numbers all other varieties of bacteria in feces. Variety D: Gas production with dextrose and lactose; 

 no gas production with dulcit, saccharose, mannit, or raffinose; indol positive, nitrate reduced. 



228 



