66 
Our parasite has received various scientific names, according to the 
fancy or opinion of authors; but, as the further history of its classi¬ 
fication is unnecessary now, I will mention but two of these: 
1st. JDcrmatoclectes ovis , sheep-itch-mite of Gerlach, by whom it was 
considered as peculiar to sheep; but the most recent authority restores 
the name Psoroptes equi, horse itch-mite of Gervais, considering the 
species infesting the horse, cattle and sheep, as identical. 
It is distinguished from the itch-mite of man (Sarcoptes scabiei , Latr.) 
by two or three important characters. The four anterior legs and two 
of the hind, at least, in the males of each species are furnished with 
sucking disks, placed on comparatively long pedicels or stems. In the 
itch-mite of man, so far as I can ascertain, these pedicels are only one- 
jointed. But the most important difference is, that the mouth of the 
human itch-mite is furnished with sharp scissor-like jaws or nippers, 
with which they can readily cut into the skin, and form their sub¬ 
cutaneous burrows. The sheep mite is furnished with comparatively 
slender, lancet-like mandibles, to the sides of which the little palpi, 
or mouth-feelers are glued, thus forming a sort of tube, one part of 
which is capable of piercing. But while this peculiar form of the oral 
apparatus enables them to pierce and suck, it deprives them of the 
power of cutting; and hence, notwithstanding the general opinion to 
the contrary, they are not sub-cutaneous in their habits, and do not 
form true burrows, as the human itch-mite. 
It lays its eggs on the surface of the skin, to which they adhere by 
a gluey matter. The length of time these require to hatch in such 
situations is not positively known; but some, placed in a bottle and 
kept to the warmth of the body, hatched in fourteen days. The young 
which are produced from these have only six legs; but, after several 
changes of skin, or moultings, they acquire eight, which is the normal 
number of the class. With the little sucking disks of their feet they are 
enabled to cling firmly to the skin of the sheep. By piercing the 
skin with their lancet-like mandibles, irritation and a species of inflam¬ 
mation of the skin follows, and an exudation takes place, which ulti¬ 
mately forms the scab. As stated by a writer on this subject, “Ex¬ 
amination will disclose spots on the skin, white and hard, the center 
marked with yellow points of exudation, which adheres to the wool, 
matting the fibre together. The wool may be firm on these spots, 
and no scabs are seen in this stage. Then the yellow moisture evapo¬ 
rates, gives place to a yellow scab, which adheres firmly to the skin 
and wool. Raw places appear at points which the animal can reach 
with its teeth and hind feet. The disease is complicated in summer 
by the presence of the larvae of the blow-fly, the maggots burrowing 
under the scab.” 
The remedies are reduced to one class—those which have for their 
object the destruction of the mites and their eggs. In addition to the 
applications of arsenical and murcurial ointments, arsenical and tobacco 
washes, which are so generally recommended, the writer from whom 
I have just quoted strongly recommends a wash of dilute carbolic acid. 
