4 FIRST LESSONS IN DAIRYING 



quarters, also as two separate glands. It is sus- 

 pended from the abdominal walls in a fibrous cap- 

 sule, and is held together by fibrous tissue. Doctor 

 Bitting has shown by injecting colored liquids 

 through the teats that the halves are again very dis- 

 tinctly divided into two parts, and that only the milk 

 produced in any quarter can be drawn from the cor- 

 responding teat. 



A longitudinal section of a quarter and teat shows 

 that the opening of the teat is guarded with a 

 sphincter muscle. A cavity through the length of 

 the teat is lined with folds of tissue, and just above 

 the teat is another cavity known as the milk cistern. 

 This is not large, holding but a few ounces, and 

 ducts open from this into the tissue of the gland. 

 These ducts divide into smaller branches, which 

 eventually end in little groups of cavities, the alveoli 

 or ultimate follicles. These alveoli are in groups 

 which may be likened to a small bunch of grapes. 

 They are lined with epithelial cells and surrounded 

 by a network of little blood vessels, which nourish 

 them. They vary in size from 1/250 to i/ioo of an 

 inch in length and from 1/1300 to 1/800 of an inch 

 in diameter. 



The blood leaves the heart through the posterior 

 artery which divides in the region of the hips. Here 

 it again divides into two arteries, the common iliacs, 

 and again into two more arteries, from which, after 

 these have divided into many small capillary ar- 

 teries, the cell tissue in the alveoli is fed. 



Milk veins. The cells use such portions of the 

 blood as they need, and capillary veins begin to 



