DISEASES Ot COWS. 441 



the ducts and become mingled with the milk. This ex- 

 plains the cause of bloody milk which is sometimes given 

 by cows, or at times becomes a permanent product of 

 - young cows whose mammary glands are in an abnormal 

 or undeveloped condition. It also explains how the sensi- 

 tive mucous membrane, abundantly supplied with blood 

 in the minute circulating vessels, when in an inflam- 

 matory condition from any cause, secretes an excessive 

 quantity of mucus, and hence we may have ropy milk ; 

 which is milk containing so excessive a mixture of 

 mucus as to become adherent and stringy. Or when 

 this ropy, glutinoUs, adherent mass fills the ducts, and 

 no milk can pass through them, the lobular masses 

 become engorged and tumefied, the udder becomes 

 swollen and hard and painful from the tension upon 

 the sensitive tissue, the gathered matter is absorbed 

 into the connective tissue and the capillary vessels, and 

 we have a development of garget or inflamed and tumefied 

 udder in its worst form. 



Unless speedily relieved, the fine secretory cells be- 

 come obliterated in a growth of hardened fibrous tissue, 

 and the gland, so far as this may occur, loses perma- 

 nently its power of yielding milk, and a part of the 

 udder may, as we sometimes find, become spoiled for 

 future use and permanently dried up. In bad cases the 

 cellular matter breaks down into pus which burrows 

 through the gland, forming an abscess, or several of them, 

 by which the products of the inflammation escape. This 

 involves destruction of the glandular substance, the lob- 

 ular masses are destroyed, and the productive abihty of 

 the udder is in greater or less part lost beyond restora- 

 tion. The structure of the teat and of the fibrous bands 

 enveloping the glands explains how the cow is able tore- 

 tain the milk or let it down, as is done in the operation 

 of milking. The whole muscular part of the udder is 

 under the control of a system of voluntary nerves. The 



