THE ITCH INSECT. 
process precisely similar to, and susceptible of, as much accuracy 
as that by which a drawing is reproduced on tracing paper. It 
must be observed, however, that in the finishing touches, and the 
most minute details, the pencil of the draughtsman must after 
all be guided by his artistic skill. To what extent this is true, is 
proved by the fact, tkat two drawings of the same object, viewed 
in the same microscope, and^ made 
with the same camera, by artists 
of different skill, will be different. 
We shall here, as in the former 
case, present the reader with some 
examples of microscopic drawings 
made by the aid of the camera. 
61. In fig. 41 is a magnified 
section of the human skin, cut in¬ 
wards at right angles to its surface, 
to the depth of about the sixth of an 
inch. The following is the succes¬ 
sion of organised parts included 
within that depth :—a the sudori¬ 
ferous gland; b c the sudoriferous 
duct, leading to the surface of the 
skin ; d the subcutaneous cellular 
and adipose tissue; e the derma or 
true skin ; f the papillae ; g mucous 
tissue or interior epidermis; h the 
epidermis or superficial skin. 
62. It is now admitted, though 
the fact was long doubted, that the 
malady called the itch in the human 
body, and that called the mange in 
the horse, are produced by an insect 
hatched under the cuticle of the 
skin ; the insect which produces the 
itch, called the acarus-scabiei , is 
represented, highly magnified, in 
fig. 42. To extract this insect, the operator must, says Mr. 
Quekett, examine carefully the parts surrounding each pustule, 
and he will generally find, in the early stage of the disease, a 
red spot or line communicating with it; this part, and not the 
pustule, must be probed with a pointed instrument, and the 
insect, if present, turned out of its lurking-place. The operator 
must not be disappointed by repeated failures, as in the best 
marked cases, it is often difficult to detect the haunts of the 
creature. 
FIG. 41.— MAGNIFIED SECTION OF 
THE HUMAN SKIN, SHOWING 
THE PERSPIRATORY GLAND, WITH 
ITS DUCT, DRAWN WITH A CA¬ 
MERA BY DR. MANDL. 
95 
