ON POULTRY LOUSINESS IN THE HORSE. 223 
coin. This bare part becomes covered with a crust of dried 
serosity, which soon exfoliates, and is replaced by a new 
epidermis, perfectly smooth. 
This primary stage of the disease is difficult to meet with, 
because, ordinarily, horses are not submitted to examination 
before depilation has commenced, the sequel of the desiccation 
of the vesicles. 
At the second stage of the poultry lousiness, the most 
pathognomonic lesion is the depilation consecutive on the 
vesicular eruption ; and this is so characteristic, that, once the 
disease observed in its true form, and traced to its cause, a 
simple coup d’ceil is all that is necessary to recognise and dis- 
tinguish it from all other cutaneous affections. 
The depilation is of that remarkable character that it reflects 
exactly, in the general impression it makes upon the skin, the 
form of the vesicular eruption, solitary or confluent, of which it 
is the latest vestige. In fact, the surface is marked by regular 
circular patches, of the diameter of a lentil, giving it the aspect 
of tiger spots. In places where the eruption has been the most 
confluent, the depilation spreads between the vesicles, and so 
extends over a considerable patch of surface ; but, even in these 
places, the circular disposition of the denuded patches, the pri- 
mary expression of the original vesicular eruption, is still main- 
tained in the smooth condition of the epidermis. 
This depilation spreads, like the vesicular eruption of which 
it is the consequence, with very great rapidity. In two or three 
days the horse with the most shining coat may have it spotted 
over with circular patches bare of hair, and in the course of a 
week will the hair and epidermis be destroyed over a large ex- 
tent corresponding to the parts where the eruption has been the 
most confluent. Such is the rapidity of the depilation that we 
are but too apt to date the disease back to a long period when 
it is, in truth, but of a few days’ duration. 
It is only at this stage of the phthyriasis that horses 
ordinarily come under observation ; and therefore does it be- 
come difficult at such a time to assign to the disease any spe- 
cific character : the vesicular kind of eruption serving to dis- 
tinguish and classify it having left no trace upon the skin save 
circulatory depilation. Sometimes, at this stage of the disease, 
sorts of solid papulae form within the substance of the skin, which 
become crowned with secondary vesicles, whose progress is 
identical with that of those we have already pointed out, dis- 
appearing after the formation and detachment of the crust suc- 
ceeding the secretion. 
During the whole of this stage, as at the first breaking out of 
the disease, the patients are tormented with continual burning 
