78 MASTITIS OF THE COW 



udder afforded less favorable conditions for development. 

 In the last case the bacterial action was quicker and more 

 widely distributed, partly because the udder was rich in 

 fluid which afforded a better nutrient medium for the micro- 

 organisms and partly because of the synchronous strepto- 

 coccic milk-infection, circumstances, so to speak, which 

 placed the tissue between two fires. 



Udder-infection 

 Bacillus pyogenes always induces a stroma-infection 

 first, and this can later develop into a secondary milk- 

 infection by perforative ulceration of the milk-ducts. 

 Therefore the stroma-infection is the most important, and 

 milk-infection is only a result of it. 



STROMA-INFECTION [Interstitial Mastitis'] 



The stroma-infection manifests a typical progressive 

 character. 



Ports of Infection. — Infection may gain entrance 

 through the teat canal, wounds, or through the blood 

 stream. Infection by way of the blood follows pyobacil- 

 losis of the lungs with penetration of a pulmonary vein by 

 a necrotic focus. Pyobacillosis of the lungs is not alto- 

 gether infrequent. It appears to be present in calves prin- 

 cipally and may cause udder conditions in yearling heifers. 

 The condition can be produced through an infected wound 

 and is not uncommon. 



Infection through the teat canal is the most common, in 

 my opinion, since the condition appears to be primary in 

 the udder without presenting any wound of the udder. If 

 the bacillus is brought to the mouth of the teat canal it can 

 enter the milk in that canal and grow in it, and then be 

 taken up by the leucocytes. In other cases a cow may lie 

 down and tlie infection be introduced on a straw which may 

 be forced into the teat canal. 



