278 
SarCoptic Scabies 
The above is a condensed account of the structure and life-history of the 
human Sarcoptes as at present known, and it is now proposed to deal briefly 
with the forms which are generally considered distinct from it. In order not 
to prejudge their status it will be as well to allude to them simply under the 
names of the animals they affect, leaving open the question as to whether 
they are species, varieties, or merely races. The characters which are supposed 
to distinguish them from the human Sarcoptes will be indicated, and anything 
else of importance to our purpose will be added. 
A good plan will be to give the Tierreich definition of each form at the 
outset. It aims at the briefest possible characterisation, and provides a con¬ 
venient starting point. 
Many of these forms have been naturally and artificially communicated 
to different animals from their proper hosts, and the matter will be referred 
to in due place, but in this connection Delafond and Bourguignon utter a 
warning which is very much to the point. Artificial attempts to communicate 
scabies from one animal to another frequently fail, but too much importance 
must not be attributed to such failure. Probably in nature there are many 
abortive attempts at invasion of another animal before success is attained, 
and in artificial infection the conditions are generally much less favourable. 
Comparatively few mites are transferred, and many of these may be unsuited, 
from their nature ( e.g . unfertilised nymphs) or from their condition through 
injury in the act of transference, to establish the disease on an animal which 
might very well succumb to repeated natural invasions. 
SARCOPTINAE PARASITIC ON OTHER ANIMALS. 
Scabiei-crustosae. 
Tierreich : Fiirstenberg, 1861. 
Dorsal scales blunt; no rugose area; notogastric spines long and pointed. 
The epiandrium reaches the epimere. 
$ 410 x 340/z. 
<? 170 x 150/z. 
Man; causing Norwegian itch. Norway, Germany, France. 
Fiirstenberg’s description is in substance as follows: 
Female. Body nearly round, not much longer than broad, the fourth 
thoracic segment prominent at the sides, the sensory hair borne on it being 
very long 1 . Back with scale-like prominences surrounded by a rim of chi tin. 
Six long notothoracic cones and 14 curved, very sharp notogastric spines. 
Male. Body nearly round; fourth thoracic segment rather prominent, 
with strong, long sensory hair. Very few dorsal scales, at the edge of the 
thorax and abdomen. A shield-like area (Abgrenzung) finely punctate and 
1 This is the third dorsal hair, the more anterior of Munro’s two lateral hairs. Fiirstenberg 
believed that folds—often conspicuous at the sides—indicated primitive segmentation. 
