Anatomy and Physiolorpj of the Mammary Gland. 101 



wise have been the one of 7ttcro-gestatiou, her mammae are filled 

 with milk ; the animal is much excited, and comports herself 

 precisely the same as if slie had been delivered of a litter of puppies. 

 This fact beautifully exemplifies the sympathy which exists 

 between all the orizans of generation, and which is alone main- 

 tained, kept in full vigour, and brought into operation by the 

 nervous system. 



bthly, Health. — A freedom from disease, either of an acute or 

 chronic character, is of the first importance to the production ot 

 milk. A cow affected with acxite disease is sure to diminish in 

 the quantity, and probably will cease entirely in her yield of milk, 

 while such disease lasts ; and even on her recovery will not give 

 anything like the amount she had previously done. It is, how- 

 ever, affections of a chronic nature which exert the most serious 

 consequences. Without threatening any immediate danger to life 

 they frequently, by their persistency, destroy the value of the 

 animal for milking purposes. Chronic diseases of the liver 

 especially are among this number. Maladies affecting the gland 

 itself will evidently exert a deleterious influence, by their direct 

 action upon its secretive power ; but otherwise they are of no 

 more serious import than diseases of the internal organs. 



Not only do organic affections thus interfere with lactation, 

 but simple functional derangement of any of the viscera docs the 

 same thing. Evidence of this is afforded in ordinary cases of 

 diarrhoea, which depend merely on some irritating or deleterious 

 aliment having entered the intestinal canal. As it is unnecessary, 

 however, that we should go into detail with regard to the several 

 acute or. chronic diseases of milking cows, or of the different 

 causes leading to functional derangement of the various organs 

 of the body, we pass on to speak of — 



dthly, Temperature. — The injurious effect of the extreme heat 

 of summer or of the cold of winter over the animal functions re- 

 quires but little exemplification. Cows exposed to either suffer 

 in their lactation. A highly elevated temperature, by keeping an 

 animal in a state of excitement, often produces functional dis- 

 orders of the liver which lead to diarrhoea, and a consequent 

 diminution in the secretion of milk ; while the opposite state of 

 the atmosphere, by depressing the vital functions, has a similar 

 result. Notwithstanding this an animal has the power of main- 

 taining a uniform heat of its body under any circumstances it may 

 be placed in with regard to temperature. This heat, which is equal 

 to about 100° of Fahrenheit, is, however, kept up with less tax on 

 the system under some circumstances than under others. As a 

 general principle a greater demand is made on some of the 

 elements of the body in cold than in warm weather. 



It is principally by the union of the oxygen of the atmosphere 



