FISTULOUS WITHERS AND POLL-EVIL 15 



erable thickening of the interdigital tissue. In this case the suppuration 

 had not extended under the nails. 



§ II. Fistulous withers and poll-evil. Recent inves- 

 tigations indicate that these very common and troublesome 

 local diseased conditions are either directly or indirectly the 

 result of bacterial invasion. This conclusion is tentatively 

 drawn from the fact that the bacteriological examinations made 

 from the pus and from recent lesions in these affections invari- 

 ably reveal the presence of streptococci or micrococci, or both. 

 Gay found a streptococcus in each of seven cases of common 

 fistulous withers and in two cases of poll-evil. It was invariably 

 associated with a micrococcus. He found in five cases of 

 deep seated shoulder abscesses M. pyogeiies aureus only. It is 

 instructive to note, that bacteria closely resembling this or- 

 ganism has frequently been found in the deeper layers of the 

 skin. The mechanical injuries commonly attributed as the 

 primary cause consist usually of little more than skin irritation 

 from ill fitting harnesses, saddles or from blows. While these 

 are mechanically not extensive, they are sufficient to liberate 

 into the juices of the subjacent tissues the bacteria deeply seated 

 in the integument. The inflammatory process leading to sup- 

 puration, the formation of fistulse, the new formation of fibrous 

 tissue in the affected parts, and even the bone necrosis occa- 

 sionally seen are all possible and rational results of the activi- 

 ties of the pyogenic bacteria found in the lesions. There is 

 nothing in their character to suggest causative agencies other 

 than microorganisms. The changes involved in the inflamma- 

 tory process, the deposition of fibrous tissue, and the abscess 

 formation all belong more proper] \- to general pathology and 

 need not be discussed here. These affections are mentioned 

 in this connection simply because the accumulating evidence 

 tends to strengthen the working hypothesis that they are the 

 result of bacterial invasion. 



§12. Infectious Mastitis. Cattle suffer frequently from 

 an acute inflammation of the udder as the result apparently of 

 an invasion by a number of bacteria. The results of the inves- 

 tigation of this affection thus far reported suggest that the 

 form which is transmitted from animal to animal is caused by 



