580 DISEASES OP THE MAMMARY GLANDS. 



CONTAGIOUS MAMMITIS IN MILCH COWS. 



Although its cause was unknown before the iiwestlgations 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 Soisson- 

 nais, 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 ex- 

 plained 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 diarrhoea. The first appreciable indi- 

 cation is a change in the milk, which diminishes in quantity, and, 

 although normal to all appearance, coagulates rapidly if left undis- 

 turbed. 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 harden- 

 ing 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 fcstid, 

 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. 



