136 PAKASITIC SKIN DISEASES. 



her venomous saliva. She then burrows underneath the scarf-skin 

 and away from her point of entrance to a distance of about half 

 an inch, so as to form, a burrow, tunnel or gallery, in which she 

 lays her eggs as she goes along. By the time a pimple forms at 

 the inoculated spot, the egg-bearing parasite has left it, and 

 cannot be found if a search be made for her in the pimple, vesicle, 

 or scab. In a white-skinned human subject (affected by itch), the 

 position of the characteristic gallery is marked on the skin by a 

 red line, which somewhat resembles the scratch of a pin; but it 

 is not visible in the skin of a horse, owing to the thickness of the 

 scarf-skin of that animal. If a pin be pushed into the gallery, the 

 parasite can be removed at the point of the pin. The male 

 parasites (which form, only about a twentieth of the entire 

 number), the unimpregnated females, and the larvae reside among 

 the crusts on the skin. Although the disease may be fully estab- 

 lished on some portions of the skin, which will consequently become 

 thickened, thrown into folds, and bald, it may be in its first stages 

 on other parts, upon which the grain-like eminences made by the 

 newly-formed crusts, can be felt among the hairs of the coat. The 

 disease takes from one to two months to become fully established. 

 Rubbing the affected surface^ and manifestation of pleasure when 

 the mangy spots are scratched with the fingers, are prominent 

 features of the complaint. 



3. The insects of the third form of mange are called symbiotes. 

 Their invasions are confined practically to the legs, and extend 

 very slowly from one part to another. They commence iheir 

 attack at the back of the pastern, and work upwards ; but rarely 

 go higher than the knee and hock, and are seldom found except 

 on coarse, hairy-legged animals. They affect the hind limbs 

 oftener than the fore, and those of young horses more frequently 

 than those of old ones. Strange to say, they manifest their 

 presence as a rule only during winter; the probable reason of 

 this being, that the excretions from the skin during the summer 

 are sufficient for their nourishment. Possibly for a similar reason, 

 namely, that the skin is more active during work the horse suffers 

 more then than in repose. The symptoms are : itching ; the 

 formation of crusts, cracks, and sores ; thickening of the skin ; 

 and falling-out of the hair. When the pasterns are affected,' the 

 symptoms may resemble those of grease or grapes (p. 156). " At 

 the commencement of the attack, the only important symptom 

 which attracts attention, is the habit the mangy horse has of 

 abruptly striking the ground with a hind foot for hours at 

 intervals when he is at rest, especially during the night. Some 

 horses kick. All scratch and bite the fetlocks '' (Friedherger and 

 Frohner). 



