383 



the milk. With regard to the bacteria of the first class, the author has 

 uotyet found any form which agrees exactly with Bacillus acidi lactici, 

 described by Heuppe. 



Several bacteria have been isolated wliicli agree with it in most particulars, but in 

 every case there has been some point of difference whicli has indicated that I have 

 not had exactly the same form. The acid formed by the various members of this 

 class is usually lactic acid, but acetic acid and formic acid have been found in some 

 cases by Mr. Dains, who has made some chemical studies of my cultures. 



[The bacteria of the second class all] liquify gelatin, and many of them pro- 

 duce spores. Butyric acid is one of the common bj^ -products of tlie action on milk. 



* * * The curd formed is not hard and fragmented, but is soft and jelly-liko 

 or sometimes divided into fine flakes. It is further found that after a few days the 

 curd begins to grow less in amount and a whey to appear. As the growth continues 

 longer, the curd is seen to be slowly dissolved, and this gradual solution may con- 

 tinue until the curd is completely dissolved into a limpid liquid. The solution may, 

 however, in some species stop short of completion, and there may be thus formed a 

 quantity of liquid in which a small curd floats. The liquid formed ditters widely 

 in different cases. It is sometimes clear and sometimes cloudy. Sometimes it 

 assumes an amber color, and in one case a brilliant yellow color was produced in 

 the dissolved liquid. At other times the liquid becomes greenish. ^ * ^ 



That the curdling of milk and the subsequent solution of the curd are proc- 

 esses independent of each _other, is indicated by the following observations: 



* ^ * Among the species which I have isolated from cream two have been espe- 

 cially interesting in this connection. The first is an organism growing into long- 

 rods, which occasionally branch and break up into short, oval, yeast like bodies. 

 It has many points of resemblance to Saccharomtjces albicans. This species has a verj' 

 characteristic growth on gelatin, forming a layer resembling ground glass, and is 

 easily distinguished from any other organism which I have found. When first 

 studied it was found that at the ordinary temperature of the room it would not 

 curdle the milk, but that it did slowly digest the casein. The milk became clear 

 and transparent after a few days, appearing exactlylike the peptonized curd of other 

 species, but without the previous i)recipitatiou of the casein. When this species 

 was grown in milk iu a warm oven, at a temperature of about 35"^ C, the curdling 

 appeared first, and the peptonizing subsequently took j)lace. After several mouths 

 of cultivation I found that this organism had lost its power of precipitating the 

 casein. Even when growing iu the warm oven the power of curdling the milk did 

 not appeal. The organism had, however, lost none of its morphological characters, 

 and it still possessed the power of j)eptonizing the casein. 



The second species is one of the forms of bacilli which would be included under 

 the general name of Ijacilius Jluorescens Uquefaciens. A number of liquefying forms 

 seem to have the power of in-oducing a fluorescent appearance in gelatin, and the 

 above name probably includes several varieties. The variety which I have isolated 

 and studied acted at first like ordinary liquefying organisms, curdling the milk 

 rapidly and subsequently dissolving the curd. This organism was kept in the 

 laboratory for several mouths and carried through a large number of cultures. 

 After 3 or 4 months it was noticed that its power of curdling milk was becoming 

 less marked, as ^t required a longer time or a higher temperature for this pnrpose. 

 Finally it disappeared altogether. The digesting power was not lost, however, 

 for the milk was peptonized as usual. 



In these two cases it is plain that we have an indication of the independence of 

 the two actions on milk, and see that one may be lost without the other. We can 

 hardly be wrong then in assuming, with all experimenters, that these liquefying 

 organisms produce two chemical ferments, one having an action similar to rennet 

 and the other an action similar to trypsin. 



