UDDER-TUBERCULOSIS 93 



Disturbance of Milk Excretion by Tubercles. — 

 The tubercles usually form in the lower parts of the udder 

 and as they develop exert pressure upon the walls of the 

 adjacent milk-ducts, inducing their collapse, obstruction of 

 milk flow and finally milk stasis [galactostasis] in the su- 

 perior parts of the udder. The tubules and finally the 

 lobules are distended by the stagnated milk. Milk con- 

 cretions may form in the dilated closed tubules through 

 resorption of water and precipitation of the less soluble 

 matter. These are exceptionally small granules which are 

 only visible with the microscope. They resemble granules 

 of starch in appearance and therefore are called corpora 

 amylacea. 



Milk stasis is seldom severe enough to induce pressure 

 atrophy, and finally rupture of the walls between tubules 

 to the formation of one large single tubule or milk cyst 

 [galactocele] by coalescence of two or more tubules. 



Ulceration of Milk-ducts. — Tubercles may destroy 

 the walls and epithelium of the milk-ducts. Direct contact 

 with the milk increases the liquid content of the tubercle 

 and in this way the necrotic area undergoes softening and 

 parts of it are finally emptied into the milk. 



In this way the tubercle bacilli, like the pyogenes 

 bacilli: (1) may be excreted with the milk; (2) be trans- 

 ported to other parts of the same quarter by leucocytes, or 

 (3) cause a secondary milk-infection by remaining in the 

 milk-ducts with the thick pulp-like mass of softened necrotic 

 material. 



The retained infectious organisms gradually induce ne- 

 crosis of the mucous membranes, which desquamate and, 

 like croupous membranes, are excreted with the milk. The 

 wound produced by desquamation of these necrotic cells 

 can become infected and thus the condition proceeds. 



Ulceration of a Blood-vessel Wall. — A tubercle 

 can destroy a vein wall in a similar manner. The altered 



