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 ; y 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. 

 Q,uekett, 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. 



95 



FIG. 41. MAGNIFIED SECTION OK 

 THE HUMAN SKIN, SHOWING 

 THE PERSPIRATORY GLAND, WITH 

 ITS DUCT, DRAWN WITH A CA- 

 MERA BY DR. MANDL. 



