THE GENUS DEMODEX. o 



Gmeiner examiued numerous cases of skin-disease (Alopecia, 

 Carcinoma, Eczema, Furunculosis, Herpes, Impetigo, Lichen, Lupus, 

 Pityriasis, etc.), and could not find specimens of Demodex in the 

 majority of cases ; when present the mites were not more numerous 

 than in the sound parts of the skin. 



Follicular manrje of the Dog*. — Perhaps the most serious disease in 

 which Demodex is found is the so-called Follicular or Red Mange of 

 the dog. In typical cases of this complaint the mites are found 

 in enormous numbers, but Gmeiner and also Mettam have shown that 

 D. canis is not the actual cause of follicular mange, which is due to 

 a bacterium [Stajfht/lococcus pyogenes alhus or some allied form). The 

 mite plays an important part in the disease, however, by preparing the 

 ground for the invasion of the bacterium by dilating the follicles and 

 sweat-glands, and possibly also carries and introduces the germ. Whilst 

 the Acari remain in the follicles or sweat-glands some of the bacteria 

 may penetrate more deeply and be conveyed from one point to another 

 by the blood-stream. The clinical symptoms of follicular mange vary 

 very greatly : sometimes it assumes a pustular form characterised by 

 numerous pustules accompanied by various crusts, etc. ; in other cases 

 it is a squamous affection with numerous epidermal pellicles, and some- 

 times tlie irritation is not very great in this variety. There is also 

 a form of the disease with circular patches accompanied by large 

 piistules. In a typical case there are small hairless patches, together 

 with reddish pimples and pustules, skin hot and thickened in the 

 affected places, etc. 



The first symptoms of demodectic mange consist of slightly reddish 

 hairless patches or spots with pustules, at the elbows, around the 

 eyes, etc. These hairless patches gradually spread, becoming redder 

 and appearing also on the inner surface of the feet and on the 

 cheeks. The eyelids become swollen and inverted and have a purulent 

 margin. The skin of the sides of the cheeks is thickened, devoid of 

 hair, and covered with various papules and pustules in varying stages 

 of irritation. Pruritus is still intermittent at this stage but more 

 marked. The malady at last becomes generalised and occupies most 

 of the surface of the body. There are numerous pustules, and in places 

 they become confluent; crusts due to the morbid secretions also make 

 their appearance. In some places the skin is moist and chapped, and 

 there is a yellowish matter in the folds of the skin. A cylinder of 



* An excellent account of follicular mange in the dog is given in Prof. L. G. 

 Neuinanu's 'Parasites et Maladies Parasitaires du C'liieu et du Chat.' Paris, 1914. 



b2 



