PRURIGO. 491 



and transparent, and that a watery liquid appears. From these pecu- 

 liarities of the nodule, and from the results of the treatment of prurigo, 

 Hebra concludes that in this disease we have to deal with a liquid 

 effusion in the deeper layers of the epidermis, which, however, is not 

 profuse enough to form vesicles, but merely produces flat nodules, at 

 first perceptible to the touch, and afterward to the eye. The subjec- 

 tive symptoms and course of the disease, especially the intolerable 

 itching which accompanies it, seem fully to substantiate the correct- 

 ness of this hypothesis, which, indeed, cannot be demonstrated directly 

 upon the dissecting-table, as the lesions described above always disap- 

 pear after death. In spite of the identity of their symptoms, it is 

 usual to discriminate between the form of prurigo provoked by lice, 

 ticks, irritating dust, and other external influences, and that very ob- 

 stinate disease known as true prurigo, which, arising without known 

 cause, often continues throughout life. "Want of proper care of the 

 skin and scanty food seem to play an important role in the etiology 

 of true prurigo, which is much more common among the poorer classes 

 than among the well-to-do. The disease appears at every age, except- 

 ing only the first years of childhood. Men are more liable to it than 

 women. 



SYMPTOMS AND COURSE. The most prominent objective signs of 

 prurigo consist in those resulting from the violent scratching, and not 

 in the nodules themselves, which are scattered and flat, and, indeed, 

 are often hard to find, although, from the irritation which they produce 

 upon the skin, they create an itching as intolerable as that produced 

 by the bites of insects, or by gently tickling the surface of the skin 

 with the tips of the fingers, or with a foreign body. Scratching with 

 the nails tears off the epidermis from the nodules ; a slight bleeding is 

 the result, and the blood effused dries into a crust. It is these innu- 

 merable little crusts which remain after the papule has disappeared 

 that form the most conspicuous object upon the skin of a patient with 

 prurigo. As scratches and papules are also induced by the bites of 

 vermin, we must always ascertain in such cases whether we have to 

 deal with lice and itch-insects, or with genuine prurigo in its stricter 

 sense. Gross errors, especially the mistaking of the itch for prurigo, 

 in persons whom one would not be apt to suspect of having the itch, 

 are of daily occurrence. One of the most important distinctive points 

 consists in the locality upon which the papules and scratches lie thick- 

 est. In prurigo the principal seat of the papules and scratched places 

 is upon the extensor side of the limbs, especially upon the legs which 

 is never the case in the itch and they are quite as numerous upon 

 the back as upon the belly. Body lice, on the other hand, lodge 

 chiolly where the shirt is thrown into folds, as about the neck and 



