44 Dairy Bacteriology. 



strated by placing cow's hairs on the moist surface of 

 gelatin culture plates. Almost invariably bacteria will 

 be found in considerable numbers adhering to such 

 hairs, as is indicated in Fig. 9. 



Dirt particles are even richer in germ life. Not only 

 is there the dislodgment of hairs, epithelial scales, and 

 masses of dirt and filth, but during the milking process, 

 as at all other times, every motion of the animal is ac- 

 companied by a shower of invisible particles, more or 

 less teeming with bacterial life. All of this material 

 contains organisms that are more or less undesirable in 

 milk. Bacteria concerned in gassy fermentations and 

 those capable of producing obnoxious taints are p.artic- 

 ularly common, so that this type of pollution is especi- 

 ally undesirable in milk. 



Amount of dirt in milk. When one remembers that 

 the larger part of fresh manure is of such a nature that 

 it does not appear as sediment, the presence of evident 

 filth in milk must bespeak careless methods of handling. 



The sediment or dirt test is used quite extensively to 

 ascertain the amount of dirt milk may contain. By 

 means of a cotton filter, the insoluble residue is removed 

 and is made evident upon a layer of absorbent cotton. 

 Milk that would show with difficulty any evidence of 

 dirt upon ordinary examination reveals such defects 

 very readily in this test. 



Exclusion of dirt. It is better to keep bacteria out 

 of milk, so far as practicable, rather than to attempt to 

 remove them after they have once gained entrance. As 

 is usual, prevention of trouble is much more easily ac- 

 complished than removing the difficulty after it once 

 occurs. 



