Here we have another variation in per cent, of fat and in total fat 

 produced, which is not due to food. 



In this connection I need only allude to the well known fact that 

 the last milk drawn from the udder is much richer than the first. In 

 the case of the Shorthorn cow that was milked hourly, the first four 

 ounces of milk and the last four ounces of the next full milking after 

 the experiment, were analyzed for fat, with the following results : 



First milk, per cent, fat, 1.36. 

 Last " " 8.04. 



The average for the milking was 3.36 per cent. 



Thus far we may say that the following circumstances affect the 

 quality of milk : 



1st. Breed. 



2d. Individual characteristics. 



3d. Period of lactation : (that is, the time since calving.) 



4th. Morning's and night's milk. 



5th. Frequent milking. 



6th. Samples drawn from fiist milk taken from udder or from 

 strippings. 



It ma} - fairly be claimed that all of these are independent of the 

 food. 



HOW IS MILK FORMED. 



Before we approach the relation between food and milk, I wish to 

 touch upon a subject which is the very foundation of all speculation 

 concerning the transformation of food into milk. 



How milk is formed no man knows, any more than we can tell 

 how the plant constructs starch from the elements of water and car- 

 bonic acid. It is sufficient for us to know that blood goes to the 

 udder, carrying those portions of the food which have been digested 

 and absorbed ; from this blood supply milk results. It was for- 

 merly held that the udder acted as a sort of filter, removing from the 

 blood those constituents which, when brought together, formed milk. 

 Looked at from this standpoint the constituents of the milk must 

 exist in the blood as it goes to the udder. Physiologists agree that 

 caseine is not found in the blood, also that milk sugar is not found 

 in the blood ; this boing true, it would seem to be a logical conclu- 

 sion that the udder could not act as a filter, removing the constitu- 

 ents of the milk from the blood, for the apparently good and suffi- 

 cient reason that these constituents are not in the blood at all. The 

 structure of the udder may possibly aid us in gaining an idea of what is 

 now believed, by the best physiologists, to be the true origin of milk. 



Starting at the teat, there is the opening through which the milk is 

 drawn ; following this upwards it leads into a more or less well marked 

 cavity, the "milk reservoir", this is not always found, innumerable 

 branches or milk ducts lead out from this, dividing and subdividing, 

 until the whole of the gland substance is traversed b}' small tubes. 

 Opening into these tubes are the true secreting parts : these are lit- 



