942 Veterinary Obstetrics 



some have believed, with apparently good reason, that there 

 are variations in the virulence of mammitis, somewhat in harmony 

 with the species of the infecting agent. As in ordinary wound 

 infection, so in mammitis, streptococci apparently lead in viru- 

 lence, while the staphylococci are believed to induce a milder 

 form of inflammation. 



The avenue of entrance of the infecting organisms is regularly 

 through the orifice of the teat. Their source of origin may 

 offer great variety, but ordinarily the infecting" organisms are 

 abundant, and only require some favorable opportunity for pass- 

 ing through the teat orifice and gaining the interior of the gland. 

 The more abundant and virulent the micro-organisms in the imme- 

 diate environment of the cow, the more probable the infection. 

 The bedding, floor and stall constantly afford more or less infective 

 material, the virulence of which may be partly dependent upon 

 the cleanliness of the stall, but in the main is not understood. The 

 dairyman may reduce the degree of filth, and hence of infection, 

 to the minimum. Accidental conditions which we do not under- 

 stand sometimes seem to cause a sudden increase of virulence or 

 volume of infection in the stable, which may express itself for a 

 time in the form of enzootic mammitis. 



In a large proportion of cases, there are good clinical evi- 

 dences of the source of origin of the infecting material. When- 

 ever a suppurating wound exists upon a teat, or some adjacent 

 part of the udder, and the pus has an opportunity to flow down 

 the teat to come in contact with the teat orifice, mammitis al- 

 most invariably follows, unless some adequate precautions are 

 promptly taken by the veterinarian to bar the entrance of the 

 infection through the milk canal. Retained and decomposing after- 

 birth, or any putrid discharge from the uterus or vagina, always 

 tends very strongly to induce mammitis. The pus flows down over 

 the thighs and udder, and thence along the teat, naturally the 

 posterior teat, and, gaining the apex of this, the infection finds 

 its way upward through the orifice in the teat, and mammitis at 

 once results. Possibly more direct and effective is the infection 

 through the teat orifice, when a retained afterbirth hangs down 

 so low that it comes in direct contact with the teat and is actually 

 pressed against the teat orifice. Or the tail, saturated with the 

 discharges from the vulva, may be lashed against the ends of the 

 teats and force the infection into the teat orifice. Not only may 



