6 Milk and Its Products 



the udder ; a comparatively slight effort is all that is 

 necessary to close the smaller vessels. Animals vary 

 greatly both in the control they possess over these 

 muscles and in their disposition to use it. Very few 

 can completely close the larger ducts, and very many 

 rarelj r exercise whatever power they do possess. Sud- 

 den fright, the presence of strange persons or animals 

 in the stable, any irregularity in the time or manner 

 of feeding or milking, and slight feverish conditions, 

 particularly sexual heat, are the most common pro- 

 vocatives to holding up milk. There are very many 

 cows that contract the habit of holding up the milk 

 upon the slightest provocation, and if the habit is 

 once formed it is almost impossible to cure it, and 

 the result is that the usefulness of the animal as 

 a milk producer is largely destroyed, for the reten- 

 tion of the milk in the udder interferes greatly 

 with the activity of secretion, and in a short time 

 permanently lessens it. 



The ultimate follicles. The milk ducts, after 

 branching and anastomosing in all directions, finally 

 end in a group of small sac -like bodies known as 

 acini, or ultimate follicles. It is in these small 

 bodies that the secretion of the milk takes place. 

 They are about l-30th of an inch in diameter, and 

 are found in groups of three to five, with a com- 

 mon outlet at the end of each branching duct. 

 In form and appearance they present marked 

 changes according to the condition of the animal. 

 During active lactation they are found in their 

 highest development. When lactation ceases, the 



