THE QUARTERLY REVIEW OF BIOLOGY 



free conditions. This recent observation 

 is in full accord with that of Durrell 

 (1914), namely that the spores of Basi- 

 sporum gallarum do not germinate in the 

 absence of carbon dioxide, and are in turn 

 stimulated by small amounts of added 

 C0 2 gas. 



Phelon, Duthie and McLeod (19x7) 

 attempted to employ oxygen-carbon 

 dioxide mixture for the aeration of 

 meningococcus cultures. Their object 

 was to prevent extreme alkalization of 

 the culture. With a gas mixture contain- 

 ing 2.0 per cent carbon dioxide it was 

 possible to maintain the culture fluid at 

 pH 7.0 and to prolong the life of the 

 culture slightly beyond that of the control, 

 which was aerated with an oxygen nitro- 

 gen mixture. 



Plastridge and Rettger (19^7) have 

 employed gaseous carbon dioxide for 

 aeration purposes in experimental diph- 

 theria toxin production. In cultures 

 which were grown in an atmosphere 

 enriched with 3 per cent carbon dioxide 

 highly potent toxin was produced with 

 regularity. Deterioration of the toxin was 

 prevented in the original culture, even 

 during several weeks of continued incuba- 

 tion. These authors have since found 

 that the filtered toxin is stable under C0 2 

 at various temperatures of storage. It 

 was further observed that the culture of 

 C. diphtheriae under increased carbon 

 dioxide tension contained many more 

 viable organisms than those grown under 

 the usual conditions. The initial H-ion 

 concentration was fairly evenly main- 

 tained during the incubation, by passing 

 a slow stream of ordinary air containing 

 from 3 to 5 per cent of added carbon 

 dioxide over the culture. 



CONCLUSIONS 



In this review, the investigations deal- 

 ing more or less with the effects of carbon 



dioxide on bacteria are given in chrono- 

 logical sequence. According to subject 

 matter, they could be grouped as follows : 



(1) Those that were concerned with the 

 destructive action of C0 2 on bacteria, pro 

 and con. The period covered here extends 

 approximately from 1877 to 191 5, though 

 some work on this phase has appeared 

 as late as 192.4, or even later. 



(z) Those investigations which deal 

 with the beneficial influence of carbon 

 dioxide, also pro and con. The beginning 

 of this second period was probably 

 signalled by Nowak's partial-tension 

 method for the cultivation of Bact. 

 abortus (Bang) in 1908, but more defi- 

 nitely in 1916, with Wherry and Oliver's 

 contribution to the study of the gono- 

 coccus, although still under the conception 

 of the partial tension idea. Chapin 

 (191 8) applied gaseous C0 2 in the cultiva- 

 tion of the gonococcus, and Cohen and 

 Fleming employed this gas in the primary 

 cultivation of the meningococcus. 



(3) Studies concerned with carbon 

 dioxide as a definite requirement. The 

 conception that C0 2 may be necessary or 

 absolutely essential to bacterial growth 

 has been very gradual in its development. 

 Vinogradsky (1890) proved that C0 2 

 is necessary for the nitrifying bacteria. 

 Lieske (1911) found the same to be true 

 for Spirophyllum ferrugineum. Wherry and 

 Ervin (191 8) were the first apparently to 

 recognize this requirement for the tubercle 

 bacillus, and their observations were 

 later confirmed by Rockwell and High- 

 berger. Theobald Smith (19x4) observed 

 that C0 2 is necessary for Bact. abortus, 

 since the organism failed to grow in the 

 presence of sodium hydrate. Valley and 

 Rettger (19Z5, 192.6, 192.7) reported that 

 complete inhibition of growth of common 

 laboratory stock cultures had been ob- 

 tained by C0 2 exclusion, and that C0 2 

 is necessary for bacterial development. 



