CLASSIFICATION OF ANATOMICAL ABNORMALITIES. 43 
branch; as development proceeds this branch should 
enlarge and become the left innominate vein, and the left 
precaval should atrophy to a fibrous cord. This has not 
occurred, and so the parts remain in their embryonic 
form—a form, moreover, which is normally persistent in 
many lower animals, prevailing largely in the Lizards, 
and also being constant in many of the Mammalia. In 
the Monotremes there are not only two precavals, but 
also a well marked connecting branch, which I have 
already referred to as becoming, in man, the left innomi- 
nate vein. 
Examples of the fifth, and last, class of abnormalities— 
reversive—are frequently found. This large class includes 
everything which, being an abnormality in human ana- 
tomy, is normally present in one or other of the lower 
animals. 
In one subject I found that the pectoralis minor, instead 
of being inserted into the coracoid process, passed over it, 
to blend with the capsular ligament, and be attached above 
the glenoid fossa of the scapula: in the dog this muscle is 
normally thus inserted. 
The humerus has occasionally a supra-condylar process. 
This not very infrequent abnormality—of which I have 
found one or two other specimens—is the representative, 
in man, of the supra-condylar foramen found in many 
of the Carnivora, especially the Felide, in most of the 
Insectivora, in the common seal, and in all the Edentates 
except Bradypus. 
In our dissecting room this winter we have met with 
two examples of the sternalis muscle, which exists in 
many of the lower mammalia. 
It is not unusual to find one or more slips connecting 
the flexor sublimis with the flexor profundus digitorum. 
In most of the lower mammals these muscles are blended, 
