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milk ingredients are but little changed. Certain foods also tend to im- 

 part objectionable flavors to milk. 



Difterent breeds of cows, as is well known, give milk of varying 

 degrees of richness. Thus Guernseys and Jerseys produce milk with 

 the highest amount of total solids, and Holsteins give milk with the 

 lowest amount. Individual cows, however, show wide differences, irre- 

 spective of breed. It is not unusual to find individual Holsteins giving 

 milk as rich as some Jerseys. 



Pure and Impure Milk. 



Pure milk may be defined as fhe natural product of a healthy cow, 

 drawn and cared for in a cleanly manner. Milk from diseased cows, or 

 cows in a low physical condition, cannot be considered as pure. Milk 

 from cows affected with tuberculosis of the udder is positively danger- 

 ous. There is still a diff"erence of opinion as to whether milk from 

 cows moderately aff"ected with tuberculous lungs, glands or other inter- 

 nal organs is positively dangerous, but in the light of present knowledge 

 it must at least be viewed with suspicion. Milk from some Holstein 

 cows does not contain over 1 1.5 per cent of total solid matter, and 3 or 

 even less per cent of fat. Such milk, other things being equal, must be 

 considered pure and healthy, only not as rich as that from other cows. 

 Milk drawn from a healthy cow is perfectly sterile, and if the proper 

 precautions are taken, it is possible to keep it for a considerable length 

 of time without change. As soon as the milk is drawn, conditions pre- 

 sent themselves which cause the mil k to change and become impure. 



Impure milk may result from dirty cows, dirty stables, dirty milkers 

 and dirty milk pails. Milk absorbs a bad odor very rapidly, and if left 

 exposed to a bad atmosjjhere will very soon become tainted. The 

 2)rimal cause of all the changes which milk imdergoes is the result of 

 bacteria. 



What Bacteria are. 



Bacteria may be defined as microscopic, one-celled plants, belonging 

 to the lowest plane of vegetable life. There are three typical forms, the 

 spherical, elongated and spiral. These forms may be likened to a ball, 

 a short rod and a corkscrew. Scientifically they are classed as coccus, 

 bacillus and spirillum. These minute plants are of course absolutely 

 invisible to the naked eye. In fact their average diameters may be said 

 to be one thirty-thousandth of an inch. The elongated form have an 

 average length of from .0004 to .001 of an inch. 



Bacteria reproduce themselves by division and by spores. By divi- 

 sion is meant that a single plant develops a cell wall within itself, and 

 very shortly separates into two plants. Spores are small round bodies 

 formed within the plant, which are thrown off and under suitable con- 

 ditions of heat and moisture rapidly develop into full-grown bacteria. 

 Bacteria multiply with wonderful rapidity. Many species under suit- 

 able conditions will reproduce themselves within half an hour. 



Bacteria find their way into milk as soon as drawn. They fall in 

 from the body of the cow, from the hands and clothes of the milker, and 



