i86 



BACTERIA IN BUTTER. 



the butter is taken out in the form of the butter granules. 

 The ease of the churning will depend upon the readiness with 

 which these drops of fat can be shaken together until they 

 fuse. 



FIG. 25. 



Fat globules of cream in the process of churning, i, in cream before churning. 'J he 

 successive figures show the gradual fusion of the globules into larger and larger masses. 



In fresh gravity cream the fat drops do not float around 

 separately in the liquid, but are bunched together in little 

 groups, as shown in Fig. 25, I. There is apparently some 

 invisible material holding the bacteria together, although the 

 exact nature of this material is not positively kno.wn. It has 

 been thought by Babcock (211) to be similar to fibrin which 

 forms in blood, and this author assumes that there occurs in 

 milk, after it is drawn, a process somewhat similar to the 

 clotting of blood. Whether this is correct has not been 

 demonstrated, but it is certainly a fact that there is some- 

 thing of a proteid nature connected with the fat drops, which 

 keeps them from floating freely (212). As long as they are 

 held apart by such fibrin-like material they will not easily be 

 shaken in contact with each other, and the churning will con- 

 sequently be difficult. The action of bacteria growing in the 

 cream has a tendency to soften this material. The lactic acid 



