III4 The Hair-Sac Mite of the Pig. [ November, 
In no animals except the dog and the pig does the Demodex 
seem to cause any troublesome skin disease; in the dog, however, 
this is very generally fatal. 
From purely zodlogical methods of observation, both Leydig 
and Megnin have come to the conclusion that the forms of Demo- 
dex described by them are at least different varieties, and the fact 
that the Demodex of man occurs in the least hairy parts of the 
body and is perfectly harmless, whereas that of the dog is found 
in the most hairy places, and may cause a fatal disease, seems to 
point to the non-identity of the two forms. 
Dr. Csokor next treats of the natural history of the Demodex 
of the sow, and by a series of measurements defends its specific 
distinctness. He sums up his table of dimensions as follows: l 
1. D. phylloides only reaches the minimum length of D. cants, 
never that of D. folliculorum. ee 
2. The length of the abdomen in relation to that of the whole | 
body is in D. phylloides 14, D. canis %, D. folliculorum 4. o 
3. The relation of the breadth to the length is comparatively 
twice as great as in the other forms. 
4. The appendages of the mouth are more robust d this | 
easier to study. ee 
5. The egg is larger and is rather oval than fusiform; ae : 
j 1 T 
footed larva is also larger than in the other two forms, W 
eight-footed larva is larger than that of D. canis, but smaller that 
that of D. folliculorum. A 
6. The differences between D. phylloides on the one hand, a 
D. canis and D. folliculorum on the other, are of much p 
extent than the difference between the two latter varieties, v 
After describing the regions of the body, he calls a 
the cuticle and the chitinous pieces which strengthen a ` 
transverse furrows on the abdomen (which is produced s- he 
sharp point posteriorly) are shallower towards the thore 
considers these as traces of segmentation. On the middle ye 
line of the thorax is a chitinous ridge which gives origi e 
pairs of transverse bars, to the outer thirds of which the by 
dages are movably articulated; the first pair of transverse . 
separates the thorax from the head completely. ie ea : 
are three-jointed, the basal joint being three-sided ; ge 
minated by five claws, of which two appear to belong to ei 
ond joint and three to the distal. - 
