670 



SCIENCE 



[N. S. Vol. XXXVIII. No. 9S4 



Franzen and Stuppuhn'' have proposed the 

 name formiase. 



The important point in Harden's compari- 

 son of the products of fermentation of Bacillus 

 coli and Bacillus typhosus lies in the fact that 

 the products are very similar, with the excep- 

 tion that typhosus leaves considerable formic 

 acid and no gas, while coli leaves little formic 

 acid and produces considerable hydrogen and 

 carbon dioxid. This suggests that an essential 

 characteristic of coli and of similar gas-pro- 

 ducing bacteria is their ability to elaborate 

 the enzyme formiase. This enzyme was sup- 

 posed to be active both in the gaseous fermen- 

 tation of sugars and of the related alcohols. 



Penfold's observation that by artificial selec- 

 tion a strain of coli may be isolated which 

 retains its power to produce gas from certain 

 alcohols while it has lost this power in its 

 attack upon sugars, has therefore a profound 

 theoretical significance. 



In addition to this Penfold seems to have 

 arrived at the conclusion that, if strains with- 

 out the power to produce gas from sugars may 

 be selected by artificial means, there is no 

 certainty that they may not arise either in 

 nature, or during ordinary laboratory culti- 

 vation, and so lessen the reliance which is to 

 be placed upon the gas test in diagnosis. In- 

 deed, if Penfold's conclusions are strictly 

 interpreted, we are no longer able to attribute 

 to an organism of the colon group, any charac- 

 teristic which may be called a fundamental and 

 immutable physiological function. 



If the theory of natural selection in any of 

 its original or modern forms is held applicable 

 to bacteria, we must perhaps admit the prob- 

 ability that bacteria are subject to variation. 

 That they do vary we will not dispute. That 

 they may be made to undergo mutations, or 

 that conditions may be imposed upon their 

 growth in such a way that selection takes 

 place in certain directions, we will not debate. 

 We do insist, however, that before it is con- 

 cluded that such mutations or selections have 

 occurred in any specific instance, the analytical 

 methods used to demonstrate these phenomena 



7 Franzen and Stuppuhn, Zt. f. Physiol. Chem., 

 Vol. 77, p. 129, 1912. 



be methods of sufficient accuracy to establish 

 confidence in the data. 



While Penfold's conclusions may be in the 

 main correct, there appear certain inaccur- 

 acies in his methods which detract from the 

 confidence such important deductions should 

 carry with them. We wish to call attention to 

 these inaccuracies not so much as a polemic 

 against Penfold, as a plea for greater care in 

 the analytical procedures of bacteriological 

 chemistry. 



Penfold in his tests of gas production used 

 the Durham tube. The Durham tube, while 

 useful as a preliminary qualitative test for 

 gas, is otherwise worthless. It is more inaccu- 

 rate than the Smith tube, whose shortcomings 

 were not only recognized by the originator, but 

 more fully pointed out by Keyes.^ 



The gravest fault of each is the retention of 

 a large proportion of COj by the medium. 

 Keyes's method of cultivating colon in vacuo, 

 and pumping out the gas for careful analysis 

 over mercury, seemed so promising that it was 

 employed with certain modifications by Rogers, 

 Clark and Davis^ in their study of the gases 

 produced by over 200 cultures of bacteria, 

 among which those which we are justified in 

 calling typical colons were abundant. 



A remarkable constancy both in total amount 

 of gas and in the ratio of the constituent gases 

 produced by colon was demonstrated. Incident 

 to this research, the gas production of a 

 typical colon when grown on various media 

 was studied. It was found that while the 

 total amount of gas obtained after 7 days' incu- 

 bation from 5 c.c. of a broth containing J per 

 cent. KjHPO^ and 1 per cent, of sugar, was 

 quite uniformly about 8 c.c, whether the 

 sugar was dextrose or galactose, the total 

 amount of gas obtainable from the same 

 medium rose to 12 c.c. when dulcite or mannite 

 was substituted for a hexose. 



If we compare these results with the graphic 

 representation of Penfold's determinations, on 

 page 489 of his second article, we shall find 



8 Keyes, Journal of Medical Research, Vol. 21, 

 No. 1, p. 69, 1909. 



9 Eogers, L. A., Clark, Wm. Mansfield, and 

 Davis, Brooke, paper about to be published. 



