CLASSIFICATION OF ANATOMICAL ABNORMALITIES. 41 
twisted upon itself, so as to form a complete circle round 
the profunda vein. To this class also belongs an extremely 
interesting specimen, found in our dissecting room this 
winter, in which the large intestine, when it reached the 
front of the left kidney, inclined to the right across the 
lower end of the abdominal aorta, and after forming the 
sigmoid flexure in the right iliac fossa, descended into the 
pelvis as a right-sided rectum. These and many others 
appear at present to be pure freaks of nature; but I am 
‘lad to think that, with increasing knowledge, the number 
of abnormalities, thus vaguely classified, will be lessened, 
until we may, perhaps, be ultimately able to include them 
all among the other more definite classes. 
As to pathological abnormalities—+. e. those depending 
upon disease or injury—although often medically or surgi- 
cally important, they possess no biological or general 
interest, and I have only mentioned them to make my 
classification complete. 
The third class—compensatory abnormalities—is com- 
posed of anatomical examples of a natural law, frequently 
shown in other forms of organic and functional life. 
In anatomy, if any part is not supplied with blood from 
the usual source, it derives it from another, or, if a muscle 
is deficient, its place is sometimes supplied by the abnormal 
formation of another one. 
For example, if the obturator artery 1s too small or 
impervious, it is supplemented or replaced by the enlarge- 
ment of a normal anastomosing branch from the deep 
epigastric, and this, which is described as an abnormal 
origin of the obturator, is of some surgical importance, as 
in a certain operation it is liable to be wounded, and give 
rise to dangerous, or even fatal, hemorrhage. 
I have met with one case, in which the flexor profundus 
digitorum gave no tendon to the little finger, and its place 
