MANGE. 



579 



rostrum, which is lyre- or horseshoe-shaped, is formed of several 

 chitinoid pieces. In Demodex phylloides it comprises : first, the 

 camerostrum, which is the base of the whole masticating apparatus ; 

 second, a pair of mandibles; third, a pair of maxillse; fourth, 

 maxillary feelers, poly-articulated and mobile; fifth, a tongue, un- 

 even and sty] et- shaped. On each side of the rostrum, and below, 

 we find also two small pimples of clear shade, which Csokor mis- 

 took for eyes. The céphalothorax carries upon both of its sides 

 four pairs of short and mobile feet, formed of three parts : hip, leg, 

 and tarsus, the latter being fitted with five chitinoid points similar 

 to claws. The lower aspect of the céphalothorax shows a median 

 stripe and four lateral transverse stripes. The abdomen is long 

 and transversely striated ; it is fringed upon its borders and pointed 

 posteriorly. The young parasites are small and narrow, and have 

 but three pairs of legs ; their abdomen is destitute of transverse 

 stripes. The eggs are cordiform or fusiform. The larvae undergo 

 three metamorphoses before reaching the adult state. 



Patholog-ical anatomy. On microscopic examination of the 

 skin we observe the demodex in the sebaceous glands (especially in 

 the neighborhood of the excretory canals) and in the upper parts of 

 the hair follicle. They exist in greater or less numbers ; thirty to 

 sixty are generally counted in a single gland, sometimes 100 to 200 

 and over. Almost all have the head directed toward the glandular 

 cul-de-sac. We find eggs and larvae mixed with the parasites. 



When the demodectes are very numerous the sebaceous glands and 

 their excretory canals are greatly dilated and sacciform ; inflamma- 

 tion begins in their neighborhood, an abundant leucocytic migra- 

 tion is produced, the periglandular tissue undergo purulent disinte- 

 gration, and small abscesses are developed upon the surface of the 

 invaded glands. Bat the process ends in suppuration only in cases 

 where the acari exist in considerable number. When they are not 

 very numerous they produce simply atrophy and the falling out of 

 the hair. 



The most serious alterations are observed in the pig. Several 

 suppurating glands may become confluent and form voluminous 

 purulent islands, which may contain as many as 1000 acari. Deep 

 ulcerations follow these abscesses, the size of which often reaches 

 that of a silver dollar. When the disease lasts for a long time the 

 skin becomes sclerotic ; it may become three to four times its normal 

 thickness. 



