TEXT-BOOK OF BACTERIOLOGY. 217 



speedily takes place. The spores are large and central, occasion- 

 ally rather broader than the bacillus, which consequently has to 

 bulge to some extent. 



The oedema bacilli are strictly anaerobic, and thrive only in an 

 atmosphere free of oxygen; they show themselves extremely sensi- 

 tive to the presence even of small traces of this gas. They grow 

 at usual temperatures and also in the incubator. 



They readily take the anilin stains; in cover-glass preparations 

 of tissue-juice the pointed shape of the ends forms a decided con- 

 trast to the anthrax bacillus. Gram's method cannot be employed, 

 since the cells lose the first stain under the influence of iodine. The 

 spores are capable of double-staining. 



As we have to deal here with an anaerobic species, we can only 

 watch its growth in our artificial media by means of special appli- 

 ances introduced for the cultivation of these oxygen-hating micro- 

 organisms. 



In gelatin the colonies are visible to the naked eye as small 

 gleaming balls with liquid, grayish-white contents. They increase 

 gradually in size without essentially altering their appearance. 

 The microscope shows the interior of such a colony to consist of a 

 close network of long threads, in which the spontaneous motion 

 can be seen, often with a low magnifying power. The edge has a 

 peculiar striped or ray-like appearance, such, for instance, as was 

 described in the case of the hay bacillus. 



On the agar plate are seen cloudy, dull-white markings with 

 irregular border. The microscope shows an intricately-branched 

 mass which spreads out like a covering of moss. 



In the deep test-tube cultures the restriction of growth to the 

 lower part of the puncture is at first clearly visible. With the 

 growth an extensive decomposition of the gelatin takes place, and 

 it is changed into a grayish-white, cloudy, dull liquid. Almost 

 always an abundant development of gas-bubbles takes place, par- 

 ticularly when the food medium contains an addition of grape-sugar, 

 which allows the micro-organisms an opportunity to display their 

 powers of fermentation. With the accumulation of gas the culture 

 slowly extends upward, till at length the free surface is reached. 

 A peculiar, disagreeable odor is always noticeable. 



In agar a bacterial growth takes place with jagged edges and 

 granulated contents, the whole widening out like a club at the 

 bottom and becoming thinner and thinner as it rises. The profuse 

 development of gas which (particularly in the incubator) generally 

 bursts the medium into separate portions ,and the already-men- 

 tioned stench are here particularly noticeable. 



