PROGRESS OF VETERINARY SCIENCE AND ART. 51 
to this^species ; so far as the legs are concerned there is no 
difference ; there is, however, some deviation in the develop- 
ment of the free filamentary organs ; see fig. 9- 
16 , Upper Woburn Place. 
(To be continued .) 
EXPLANATION OF PLATE I. 
Parasites of the Skin of Man and the Domestic Animals. 
Fig. 1. — The acarus of scabies in the horse, Acarus equi. It is the dorsal 
surface of the male, after Hering. Tarsal discs present on 
all the legs, with the exception of the fourth pair, which 
terminate each in two short hairs. Acarus equi is known 
from all others, by the two processes from the hind part of 
the body, best seen at fig. 2. 
— 2. — The posterior part of the body of a male viewed, upon its 
ventral aspect, after Wilson, a a. The third pair of legs 
of remarkable size, deficient of filamentary organs, but pro- 
vided with tarsal discs. The fourth pair of legs are smaller 
than in the female, and without tarsal discs, b b. Two supra- 
caudal organs supporting three long filaments on distinct 
tubercles, c. Two sucker-like organs, apparently serving 
the office of claspers. 
— 3, — The female of Acarus equi , representing the abdominal surface. 
Tarsal discs are present on all the legs, with the exception of 
the third pair, which are provided with two long filamentary 
organs. (E. Wilson.) 
— 4, 5. — Acarus cynotis , from canker in the ear of a dog, after 
Hering. The fore feet projecting straight out anteriorly, 
of equal length and size, with five joints, and both pairs 
provided with short pedicled tarsal discs. The third pair 
of feet, short, thick, indistinctly jointed, terminating in two 
bristles. The fourth pair, about one fourth, the length of 
the former, not quite visible from above, terminating in 
two short hairs. Natural size, 009 to O'lO of a Paris line, 
their greatest breadth 0’07- 
— 6. — The acarus of scabies in the ox, dorsal surface of male, after 
Hering. The fourth pair of feet with tarsal discs ; the third 
provided with short tarsal discs, and a long hair. Two pro- 
cesses from hind part of body, armed with four filamentary 
organs. 
— - 7. — Ventral surface of the female of Acarus bovis, still after Hering. 
The third pair of legs without tarsal discs, but provide 
with two long filamentary organs. 
