546 HILDA HEMPL HELLER 



acid-producing group non-proteolytic or saccharolytic. The organ- 

 isms studied by von Hibler were all energetic in their reactions. 

 B. Novyi and organisms related to it, such as B. oedematiens, 

 form hydrogen sulfide in blood media and do not produce much 

 acid in milk. They do not pep'tonize casein or blacken or 

 putrefy meat. They and the Bijermentans type and certain 

 other organisms that I have encountered do not fit so nicely into 

 von Hibler's scheme that we can safely place them in either 

 group without drawing a dogmatic line and measuring their 

 activities accurately. Douglas, Fleming, and Colebrook de- 

 scribe a sporulating anaerobe, B. cochlearius, which shows no 

 marked properties that unite it with either of von Hibler's groups. 

 It therefore seems advisable to define conditions under which 

 anaerobes may be tested to determine their affinities with these 

 two groups. Objection may be made to such a separation of 

 the anaerobes on the grounds that when borderline organisms 

 are in question it is but a cataloging process to separate them. 

 Perhaps so, but when a classification is developing as is this 

 one and when so very few borderline forms are known, a catalog- 

 ing classification is better than none; later a group containing 

 these organisms may be formed if necessary. I\Ioreover the 

 vast majority of anaerobes do fall definitely into one or the 

 other of these two groups and can be placed where they belong 

 on the basis of their behavior on ordinary media. 



The requisites governing the selection of a medium for such 

 a purpose are definite. In the first place all anaerobes must 

 grow upon it. Blackleg organisms usually refuse to grow on 

 simple sugar media. In order to give the organisms a good 

 start, and to furnish material for the formation of acid, our 

 medium should contain a little sugar, of the sort available to 

 the greatest possible number of anaerobes: glucose is probably 

 the sugar which best fulfills this requirement. But this sugar 

 should be little in amount, and sufficient protein should be 

 present, so that the acid formed from the sugar may not inhibit 

 the growth of the organisms and prevent them from carrying 

 the reaction back to an alkaline end point if they are capable of 

 so splitting protein that they produce such an end point in the 

 absence of acid. 



