C. Warbuiiton 
209 
true cause of man’s persistent scabies exists, not in contagion between diseased 
and healthy man, but in the frequent transmission of this disease to man by 
animals.” 
Gerlach’s treatise is important (for our purpose) chiefly for its study of 
the horse Sarcoptes and its comparison with that of man, and for his descrip¬ 
tion and figures of the Sarcoptes of the dog and the pig. He gives a figure of 
the burrow or gallery of the human itch-mite (very adversely criticised by 
Delafond and Bourguignon) and in some respects his illustrations are among 
the best, if minute detail be not looked for. 
Out of 230 folio pages of Fiirstenberg’s remarkable work no fewer than 
170 are occupied by a truly wonderful digest of the writings of every author, 
from Aristotle downwards, who had hitherto dealt with the subject. The 
portion of the treatise which especially concerns us is not extensive, but it 
is extremely important because of the minute detail with which the skeletal 
tissues and the armature of scales and spines are dealt with, the figures being 
drawn by aid of a “ camera clara” of his own construction. Some of his 
drawings of dorsal scales and cones are magnified 700 times. Nevertheless in 
many of his figures he makes the extraordinary mistake of giving his Sarcoptes 
two pairs of chelicerae! 
Of subsequent writers two of the most important are Robin who in 1869 
published his Memoires sur diverses especes d’ Acariens de la Famille des 
Sarcoptides, and Megnin, who, among numerous brochures on the Acarina, 
contributed several which dealt especially with this group. 
All the writers of compendia on parasitology of a later date (L. G. Neumann, 
Blanchard, Railliet, Brumpt, Neveu-Lemaire, etc.) have necessarily dealt 
with the subject as far as the scope of their work permitted, and some of them, 
, notably Railliet, have made original contributions to our knowledge. From 
a purely medical point of view the literature has become immense, but with 
this aspect of the matter we are not here especially concerned. 
Classification and Morphology of the Sarcoptinae. 
There is as yet no generally accepted classification of the Acarina. Very 
much work has been done of recent years in certain groups, and a few have 
been monographed. There is, indeed, substantial agreement as to the general 
affinities of the various members of the order, but the widest differences exist 
as to the rank to be attributed to its subdivisions. Thus while Canestrini 
(Atti 1st . Veneto, n. 1891) admitted 34 families, Trouessart (Rev. Sci. Nat. 
Ouest, ii. 1892) allowed only ten. 
To come at once to the group with which we are especially concerned, the 
term Sarcoptidae has quite a different scope as employed by different syste- 
matists. Canestrini and Kramer (Schultze’s Tierreich , 1899) use it in the 
widest sense, making it equivalent to what Banks (1904) and others regard 
as the super family Sarcoptoidea, while their Sarcoptinae are the whole family 
of Sarcoptidae as understood by the latter school, and include the following 
