7G0 ECTHYMATOUS SKIN DISEASES. 



earlier and less distinctive, and, in its milder manifestations, 

 may be confounded with impetigenous eczema; it is, how- 

 ever, peculiar and distinct in this, that, under favourable con- 

 ditions, it is undoubtedly liable to propagate from the diseased 

 to the healthy, and occasionally takes the character of an 

 epizooty. It is also much oftener encountered than the non- 

 contagious ecthyma, and may show a particular tendency to 

 the vesico-purulent character. 



Clinical History, etc. — This most frequently encountered form 

 of ecthyma, the contagious, is sometimes spoken of by the name 

 of the ' American skin disease ' of horses, from its being largely 

 observed at a period some years since, on the influx of horses 

 from the United States and Canada. 



It is more frequently met with in foreign horses, and amongst 

 those which have had close contact with these, than in others 

 differently circumstanced. It is disposed to appear chiefly 

 over the back and along the quarters, where harness and straps 

 come more closely in contact with the skin. The papules or 

 elevations, which appear to spring from the superficial layer of 

 the true skin, take a week or more ere they arrive at maturity. 

 Karely in any of the papules do we find a well-defined vesicle 

 or bleb ; at first, in some, there may be an exudation from the 

 summit of the elevation of a straw-coloured sticky fluid, which, 

 after some days, is mingled with pus-cells. The larger number 

 of these pustules come out during the first week, with occa- 

 sionally a smaller number following. When matured, the 

 elevations are considerably raised above the general level, 

 round, not running into each other, but separate and distinct, 

 with a well-marked point. 



The power of propagation which this form of pustulation un- 

 doubtedly possesses, both mediately and immediately, has been 

 conjectured to be dependent upon the existence of a specific 

 organism, plant, or animal. Although, however, fungi have 

 been detected in the pustules, it would seem that these only 

 exist in connection with the crustaceous stage, having been 

 deposited as spores from the air, and retained by the dis- 

 charges, seeing their existence has not certainly been demon- 

 strated in the pustule or vesicle previous to its rupture. 



In both contagious and non-contagious forms, the pustules 

 are distinct and hard, situated on an inflamed and tender base: 



