94 CLINICAL BACTERIOLOGY AND 



may be so deficient that a complete regeneration of them 

 is required. For the performance of this function, Ave must 

 look to vaccine - therapy to stimulate the deficiency and 

 supply that which is wanting. 



The fact of an animal showing symptoms of poll-evil or 

 fistula to the skilled practitioner is suggestive of one 

 of three conditions : Either the patient's opsonic power to 

 the causative bacterium is too low, indicating a deficiency of 

 opsonins, or the specific infection is a very virulent one, or 

 both. 



At first sight it seems rather strange that cutaneous 

 bacterial invasion should select the poll and the withers of 

 horses as the most common seats of entrance. It may be 

 there are three distinct forces at play to account for this : 



1. Some localities show a larger percentage of cases of 

 fistula and poll-evil than others. In these districts one 

 invariably finds bad stables and low roofs and unhealthy 

 surroundings, with deficiency of sunlight. 



2. Heredity plays an important part. We have known 

 three generations develop poll-evil and fistula, i.e., the dam, 

 the daughter, and the grandson, the latter poll-evil only. 

 In our experience the opsonic power to cutaneous bacterial 

 infections is markedly low in some families compared with 

 others. 



3. The bacterium most commonly found in purulent poll- 

 evil and fistulous withers is the Staphylococcus albus, in 

 our experience, and as a pathogenic microbe it may 

 be defined as ubiquitous. Certainly the horse's skin, 

 harness, etc., harbours this organism very successfully. 

 Anatomically the poll and the withers are the most prominent 

 points in horses; it therefore follows with low roofs, etc., 

 bruising is more liable to take place in these regions. One 

 sometimes sees in practice an animal receiving a blow or a 

 bruise in these parts ; an inflammatory swelling takes 

 place, but in a few days disappears. This the writer does 

 not call poll-evil. Clearly here the skin has not become 

 broken nor bacterial inoculation taken place ; but, on the 



