CHAPTER VII. 



EXTERNAL INFLUENCES WHICH ACT UPON MILK. 



(a) Their effect upon the body, thereby influencing milk 



secretion ; 



(b) Their effect upon milk after its secretion. 

 Although our knowledge, relative to the development of the 



individual components of milk from the substances in the blood, 

 scarcely extends beyond the border of hypothesis, nevertheless it 

 is established that milk formation is dependent to a certain extent 

 upon the feeding, although only within limits denned by the breed, 

 family, individual, lactation period and age. 



Through outside conditions, those factors of production are 

 especially influenced, which are themselves subject to variations, 

 especially the quantity of milk and fat content, less so the proteid 

 and sugar content, and only very slightly the salt content. 



The influence of feeding could be explained by reasoning that 

 the gland increases its activity at the moment in which a larger 

 quantity of nutritive substances circulates in the blood, after the 

 ingestion of large quantities of easily digested food. This sup- 

 position could be even enlarged upon by considering that the activ- 

 ity of the cell is stimulated by specific substances in the food in 

 such a way that it assimilates to better advantage and in increased 

 quantities the necessary constituents which it draws from the 

 blood. 



From practical experience and scientific experiments it must 

 be considered as established that the milk produced is dependent 

 both in quantity and quality, upon the quantity of digestible food 

 and on the presence of specific substances which stimulate milk 

 formation. 



This view has been accepted for a long time by practical dairymen,' who for 

 instance have observed that clover hay, in spite of its greater nutritive contents has 

 not come up to the value of good meadow hay; that meadow hay cannot be replaced by 

 a mixture of straw and concentrated food mixed in a way to make its nutritive value 

 equal to the meadow hay; further that sweet hay proves a better milk producer than 

 sour hay with equal nutritive value, etc. The value of individual pastures also shows 

 wide differences in the production of milk, although examination of the grasses of the 

 pastures gives similar results. In these investigations however it was found that beyond 

 certain limits the influence of nutrition was no longer usable, and that with sufficient 

 feeding of wholesome and tasty food no influence could be exerted upon production 

 through increased rations. 



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