716 STENOSIS OF THE TEAT DUCT. 



(10.) STENOSIS AND CLOSURE OF THE TEAT DUCT. 



In cows and these alone usually demand our attention — the teat 

 only possesses one opening, at which point the skin is reflected to cover 

 the lower end of the duct. At the point where the skin becomes continuous 

 with the mucous membrane, i.e., about |- of an inch above the end of the 

 teat, lies a sphincter or valve, which, like the greater part of the teat, consists 

 of muscular fibres. 



Stenosis of the mammary duct in cows results either from proli- 

 feration of the well-developed epithelium lining it, or from contraction 

 of cicatricial tissue. The former of these conditions occurs while the 

 animals are "dry," and stenosis only appears after the next calving. 



Occlusion of the duct is sometimes congenital in cows, or results 

 from inflammation at the lower end of the teat. Diseases of the 

 skin, cowpox, aphtha, ulcers, injuries, &c, may cause adhesion and 

 obliteration of the opening of the duct and of a considerable pro- 

 portion of its length. More frequently chronic inflammation, 

 occurring during mastitis, causes stenosis or complete occlusion ; 

 finally, the opposing walls of the mammary duct and lower portion 

 of the galactophorous sinuses may become adherent. 



Tumours sometimes foim in the upper portions of the milk duct, 

 or folds of mucous membrane may be so disposed as to obstruct 

 the flow of milk. The constriction or valve above referred to is 

 not constant in character ; sometimes it is represented by a fold of 

 mucous membrane, but in other cases there is only present a circular 

 arrangement of muscular fibres of the nature of a sphincter. 



Jensen examined 2,048 teats (cows'), with the following results : 



In 84 cases there were accessory portions of gland within the 

 wall of the galactophorous sinus. 



In 7 cases there w r ere circular folds of mucous membrane. In 

 28 cases the walls of the teat were very thick, and the sinuses small. 

 In 53 cases there was a nodular epithelial thickening at the margin 

 between the duct and the sinus. In 3 cases there was a vertical 

 dividing wall in the sinus. In 1 case there was doubling of the teat 

 (congenital). In 1 case there were small accessory sinuses. In 

 6 cases there were traumatic injuries. In 9 cases there were 

 ulcerations in the mucous membrane of the sinus. In 221 cases 

 there were cicatrices in the mucous membrane of the sinus. In 

 97 cases there were papillomata in the mucous membrane of the 

 sinus. In 9 cases there were fibrous enlargements in the mucous 

 membrane of the sinus. In 37 cases there was thickening of the 

 mucous membrane of the sinus. In 16 cases there was formation of 

 septa in the sinuses. 



