40 
The Classification of ANATOMICAL ABNORMALITIES. 
By A. Warp Co.ttins, M.B., 
ANATOMICAL DEPARTMENT, UNIVERSITY COLLEGE, LIVERPOOL. 
[Read 12th March, 1887.] 
It is impossible, in a short paper, to consider at all fully 
all the varieties of human anatomical abnormalities, and 
therefore I only intend to give a concise classification of 
them, and to illustrate the different classes by a few 
examples taken from cases or specimens which have come 
under my own observation. 
An abnormality may be defined as any deviation from 
the normal, or average, structure of a part. 
Abnormalities vary, as to their frequency (in fact some 
minor abnormalities are so often present, that it is some- 
times doubtful what should be considered as being normal,) 
and as to the extent of their departure from the usual 
formation; but whatever the nature or degree of an 
abnormality, it may be included in one or more of the 
following five classes :— 
1. Apparently purposeless abnormalities. 
. Pathological abnormalities. 
. Compensatory abnormalities. 
Abnormalities due to persistence of embryonic form. 
Reversive abnormalities. 
or Oo WO 
The large class of apparently purposeless abnormalities 
includes all those for whose existence no reasonable 
explanation can be found. Such are the cases of high 
division of the great sciatic nerve, or the case (which I 
have already published) in which the radial artery was 
