INFLUENCE OF DISEASE UPON MILK 105 
runs a subacute or chronic course; (2) parenchymatous 
mastitis, which is purulent and acute, and which is some- 
times accompanied by abscess formation and gangrene, 
and (3) interstitial mastitis, which may be a simple in- 
flammation or a phlegmonous condition. The three forms 
differ in the type of the inflammation (acute or chronic), 
the part of the udder tissue affected, the effect upon the 
milk secretion, and in the character of the bacteria con- 
cerned. One form may be associated with another. The 
disease is commonly called “ garget”” by dairymen and 
farmers. 
1. Catarrhal Mastitis—From a hygienic standpoint, 
catarrhal mastitis is of greatest importance because it 
occurs more frequently than the other forms and also 
because the milk may contain the causative bacteria be- 
fore clinical symptoms or marked changes in the milk 
are apparent and for a time after they have disappeared. 
This latter circumstance has been the inspiration of 
numerous efforts to discover a method of examining milk 
by which this disease could be detected in its incipiency. 
Catarrhal mastitis is a mucous or purulent catarrh 
of the mucous membrane of the teat canal, milk cistern, 
and large milk ducts. It is frequently accompanied or 
followed by a productive inflammation of the submucous 
and interstitial connective tissue, in which case it often 
terminates in atrophy of the gland tissue and loss of 
function. It is usually caused by streptococci of varying 
degrees of virulence; sometimes, but not often, mucous 
catarrh occurs without the intervention of bacteria from 
the effects of cold or overfeeding. The symptoms are 
never pronounced. The history of the cow is of great 
assistance in detecting incipient cases, although it is 
sometimes difficult to obtain. A statement that the cow 
