Directions for its performance will be found in Möller and Dollar’s “Regional Surgery” (uniform with the present volume), p. 454.
CONTAGIOUS MAMMITIS IN MILCH COWS.
Although its cause was unknown before the investigations of Nocard and Mollereau in 1884, this disease is of very common occurrence in England, in large dairies in the environs of Paris, and is also seen, though more rarely, in Normandy, in Brie and the Soissonnais, causing serious losses on account of its transmissibility.
It had been described in Germany by Gerlach as early as 1854, and Kitt in 1885 recognised it as common, and proposed for it the title of “contagious catarrhal agalaxia.” It also occurs in Denmark, Italy, and England.
Contagious streptococcic mammitis of cows always assumes a chronic form, during the course of which indurated centres appear, varying in size between that of a hazel-nut and a walnut.
Causation. The cause is always to be found in contagion, the disease being due to a streptococcus, which has been carefully studied by Nocard. Its transmission from a diseased to a healthy udder is explained by the fact that the milkers are careless as to cleanliness, and thus directly convey the germs to healthy teats and facilitate infection.
Symptoms. As in chronic mammitis, general symptoms are not well marked, though some cases are ushered in with cough, slight nasal discharge, and offensive diarrhœa. The first appreciable indication is a change in the milk, which diminishes in quantity, and, although normal to all appearance, coagulates rapidly if left undisturbed. Infection has already taken place, although nothing can be detected on examining the udder.
Next appears a nodule of hardened tissue above the teat. This nodule is of rounded or ovoid shape, ill-defined towards its periphery, and it becomes progressively enlarged without any sign of acute inflammation. The milk becomes watery and of a bluish colour. Microscopical examination reveals numerous streptococci. The hardening process proceeds slowly. At the end of several months the sclerosis may only have extended to one-third of the height of the infected quarter. With the appearance of these lesions the character of the milk again changes. It becomes yellowish in colour and fœtid, and contains a fibrous reticulum, whilst its reaction is distinctly acid. The lesions, which at first had been confined to one quarter, successively extend to the others unless precautions are taken.
Lesions. The lesions consist in mammary sclerosis, with nodules which progressively increase in size. This sclerosis originates in the galactophorous canals, and extends first to the periphery, then to the interstitial connective tissue; the latter undergoes hyperplasia and confines within its tracts the true glandular elements, destroying their secretory power. Locally, catarrhal mammitis exists.
The lesions can easily be recognised on microscopic examination, and, when the section is suitably stained, numerous streptococci can be detected in the acini, which are blocked with proliferating epithelial cells. These lesions are due to the invasion of colonies of microorganisms, which spread from below upwards.