158 MEDICAL ZOOLOGY. 



is pointed, somewhat carved, and when not in use is received into an oblique 

 groove, with irregular dentated margins, situated on the opposite side of the 

 prolonged portion of the organ. 2d. The maxillae, these are small, nar- 

 row, and curved from without inwards. Their base is articulated to a small 

 square piece, the chin. Their palpi are large pieces supported by the max- 

 illae, curve-pointed, and composed of three unequal joints. The terminal 

 joint, which is the smallest, presents externally a single long hair, while 

 the middle joint has two. 3d. The labium ; this is nearly triangular and 

 somewhat pointed. Toward its base and on both sides there is very long 

 hair. 4th. The tongue; this is lancet-shaped, and placed in median line. 



The resophagus is long and straight. Arrived at the anterior third of the 

 body, this canal terminates in an oblique rcniform stomach, transparent and 

 diffi cult to observe. Intestine short and slightly undulating; it contains a 

 number of brown granules, which occasionally accumulate toward its term- 

 ination. Respiration effected in skin. Sexes on separate individuals. Male 

 smaller, more oblong, flatter, of a darker color, and more active ; the ros- 

 trum is proportionately smaller and less triangular ; they have not so many 

 horny appendages on the dorsal surface. The anterior feet extend beyond 

 the anterior third of the body, reaching nearly to its centre ; the posterior 

 limbs are not so wide apart ; the third pair of feet are furnished with longer 

 hairs ; lastly, the fourth pair are much shorter, and have ambulacra furnished 

 with a sucker. The genital apparatus is placed toward the middle of the 

 body, near the third pair of limbs. The testicles are simple, the vas deferens 

 with two median glandular bodies attached ; the penis of tolerable length, 

 contained within a groove ; genital pore a little in front of the posterior 

 margin of body. Males fewer in number than the females, the proportion 

 being about one of the former to ten of the latter. 



With the female the genital pore is situated on ventral surface at a short 

 distance from the sternal plates. It communicates with a granular body 

 hardly discernible except at the period of reproduction. The female is ovip- 

 arous, laying one egg at a time. The young Sarcoptes are active, and pos- 

 sess but six legs. (Moquin-Tandon.) 



S. scabei. 



DEMODEX. D.folliculorum. Body grayish white, semi-transparent; head 

 compounded with thorax (cephalothorax) ; rostrum small, two lateral palpi 

 with sucker placed between them; last terminal joint seven palpi notched; 

 lip tvfro slender pieces ; abdomen vermiform ; feet of three joints, last provided 

 with three hooks, one long, two short ; young animal with six feet ; eggs ellip- 

 tical ; $ oviparous three varieties seen in relation to development of abdo- 

 men, either shorter than, as long as, or longer than cephalothorax. 



Habitat. Sebaceous follicles efface, nose, and auditory canal. 



Measurements. ju V'to TO V"* n length, and from yiY" to T 3 ff '"in breadth. 



Simon and Ilenle found them in ext. aud. meatus. Found present in one 

 in ten individuals. Greasy freckled faces more liable. Live in colonies, 

 fifteen to eighteen being found in a single follicle. 



