On diseases of the skin / by Erasmus Wilson.

  • Wilson, Erasmus, Sir, 1809-1884.
Date:
1851
Catalogue details

Licence: Public Domain Mark

Credit: On diseases of the skin / by Erasmus Wilson. Source: Wellcome Collection.

    586/608 (page 502)
    cylinder [tarsus] as long as the entire leg, and terminated at its extremity by a foot divided on its sole into five lobes. The head and four anterior legs are covered by a strong case of dry tine, which presents the ordinary colour of insect cases— namely, a brownish red. The plastrum is slightly tinted with a similar hue, but the three crests formed by the hip-pieces are, in virtue of their thickness, of a deep colour. These are the red lines of Gras, Raspail, and others. The posterior legs have but a thin case of chytine, and are less deeply coloured. The coloured covering of the head and legs contrasts very strongly with the yellowish white of the body of the animal. The posterior legs spring from the posterior part of the thoracic segment of the animal, two on each side ; they are conical in form, composed of three segments, and each leg is connected to the body by means of a triangular and flattened hip-piece. Each posterior leg is terminated by a rudimentary tarsus and foot, and by a long membranous hair-like organ, which is directed backwards. I have already alluded to the cleft on the posterior part of the abdominal segment of the animal, and the papilla which bounds the anal opening posteriorly. A pair of hair-like filaments sur- mounted on short tubercles are found on each side of this opening, near the posterior margin of the abdomen. These four filaments, with the four hair-like organs of the posterior legs, and the four directed backwards from the lateral part of the thoracic segment, form the twelve hair-like filaments which are observed along the posterior margin of the animal. These filaments, together with the hairs, spines, and tubercles situated on the dorsum, serve most effectually to prevent the retrogression of the acarus along its / cuniculus, while the anterior part of the creature is equally well organized for advance. I have not been able to distinguish any sexual differences between the animals I have examined. In a sketch before me is drawn a conical projection in this region, but I have not as yet seen that appearance repeated. The ova I have seen, and I have preserved a slide, on which there are two of these bodies. The internal organization of the animalcule is obscured by the large collection of adipose cells which form its superficial stratum.