ACARUS SCABIEI. 27 



arrive by tliis means a little later at the level of t]^e nervous 

 papillae, they attack these directly or indirectly, and produce a 

 fine, pricking pain, which is either repeated or remains quiet for 

 a considerable time, and which we denominate biting. The 

 deeper the bite goes, the more abundantly does the exudation 

 pour itself out in consequence of the reaction between the cutis 

 and the youngest laminae of the epidermis ; this elevates the mite, 

 and also occurs in its stomach as a colourless paste. In general, the 

 more abundant the nutritive material furnished to the mites, the 

 less do they penetrate, and the less do they plague with biting. 

 The younger the mite is, the younger is the epidermis which it 

 requires for its nourishment, and therefore the young penetrate 

 most deeply, irritate, gnaw, bite, and produce the strongest reaction 

 and exudation. Young mites, however, when they find a suffi- 

 ciency of nourishment, remain more at the surface; older mites, 

 also, in one and the same gallery, sometimes go deeper, probably 

 when there is a deficiency of nourishment for them, and even 

 have blood in their stomachs. Here and there, in the larger 

 galleries, when laid bare and rendered transparent, there is an 

 extensive exudation ; but when the mite remains at the sur- 

 face, no exudation is produced. Where the epidermis is very thin, 

 as, for example, on the generative organs, the mites pass deeper 

 towards the cutis, in order to bore into it, by which the 

 exudation becomes rich in fibrine and traces of blood. Besides 

 the shooting and evanescent sensations of pain, little is ob- 

 served at first externally of the mites which have immigrated 

 into the epidermis. They remain in the galleries, advance 

 further in a horizontal direction, or wander out and enter afresh 

 at another place. The most restless are the six-legged young 

 before they change their skins, and the maturer males, which 

 rarely remain in the same place longer than one to three days ; 

 and the galleries of which, therefore, are seldom ]'" in length. 

 Fecundated females bore further in their galleries, just as females 

 after the third change of skin, usually make themselves a long 

 passage. 



But \vhether the mites remain or emigrate, wherever their bite 

 goes deeper, there is always formed an exudation in the course of 

 a short time in the normal skin ; and this, usually on the second 

 day, elevates the epidermis with the gallery of the mite into a 

 papilla or vesicle. From the fifth day the vesicle begins to dry up 

 slowly ; the epidermis scales drop off, and the itch-process has been 



