38 CANADIAN DAIRYING. 



The glands consist of tissue, fat, nerves, arteries, 

 and veins. The secretion takes place in the lobules, 

 which are made up of from three to eight vesicles 

 grouped together. These vesicles are lined with cells 

 having a common outlet These outlets, or tiny 

 ducts, connect with other ducts, and finally empty 

 into the sinus or milk-cistern placed in the upper 

 part of each teat. From the milk-cistern the milk 

 passes through a teat-canal to the opening 'at the 

 bottom of the teat. This opening is closed with a 

 muscle. When cows leak their milk it is due to the 

 muscle being too weak. When cows are hard to milk 

 this muscle is too tense, or there may be obstructions 

 in the teat-canal. There is no remedy for the latter. 

 A sharp three-edged knife may be used to release the 

 tension of the muscle in bad cases. 



The glands are not equally active at all periods of 

 life with the cow. The call upon the dam to provide 

 nourishment for her offspring is the first stimulant to 

 milk secretion. Withdrawing the milk by the calf, or 

 by the skilful hand, is the second cause of stimulation. 

 The secretion of milk is usually most active during 

 the third, fourth, fifth and sixth lactation periods, but 

 may continue active up to the tenth or twelfth. 



Various explanations have been given of the secre- 

 tion of milk, none of which is satisfactory. The 

 metamorphic theory assumes that milk is formed by 

 the decomposition of the cells of the gland. An 

 objection to this theory is that with cows giving a 

 large quantity of milk the glands would have to be 

 built up several times during the day, which is im- 

 possible. 



