STENOSIS AND CLOSURE OF THE MAMMARY DUCT. 
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Prognosis depends on the degree of the disease. If the udder alone 
be invaded, recovery may follow operation. Otherwise, nothing can be 
done, and the animal must eventually be slaughtered. 
Treatment generally necessitates amputation of the udder. Potassium 
iodide treatment has hitherto proved unreliable. 
(3.) STENOSIS AND CLOSURE OF THE MAMMARY 
DUCT. 
In cows—and these alone usually demand our attention—the mammary 
duct only possesses one opening, at which point the skin is reflected to cover 
the lower end of the duct. At the upper end of this canal, which is from 
la to £ inch in length, the mucous membrane begins, and lines the galacto- 
phorous sinuses up to their termination. At the point where the skin 
becomes continuous with the mucous membrane, i.e., about f 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 proliferation 
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 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, injuries, &c., may cause adhesion and obliteration of the opening 
of the duct and of a considerable proportion of its length. 
In the upper sections tumour formation occurs, and sometimes folds 
of mucous membrane project into the lumen of the duct and produce 
closure. 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 form 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 
musccular fibres of the nature of a sphincter. 
Jensen examined 2,048 teats (cow’s), with the following results : 
In 84 cases there were accessory portions of gland within the wall of 
the galactophorous sinus. 
In 7 cases there were 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 sinus. 
