44 LIVERPOOL BIOLOGICAL SOCIETY. 
but as the scale is ascended the two muscles become more 
and more distinct, until in monkeys they are usually 
separate (the Aye-Aye, however, having a connecting slip), 
and in man any connection is abnormal. 
The biceps flexor cubiti, as its name implies, has 
usually only two heads of origin, but occasionally a third 
head is found. I have met with several examples of this, 
and in one of them the third head arose from the lower 
end of the pectoral ridge of the humerus. This third head, 
arising from this position, is constant in one of the Anthro- 
poid Apes, the Gibbon. 
It may be noticed that one or two of the abnormalities, 
which I have placed in the compensatory and embryonic 
classes, might also be included amongst the reversive. 
More particularly with reference to the embryonic class 
this is easily understood, as during development the human 
embryo passes through stages closely resembling, in 
many details, the adult condition of the lower mammals. 
So much is this the case, that it is as easy to conceive 
that one of these same lower animals should in time reach 
a state of evolution as high as our own, as that this embryo 
should develop into a man—instinct with life and reason. 
In one subject no less than seven examples of muscles 
peculiar to apes have been found (J. Wood), but in addition 
to these occasional similarities, we must remember that so 
closely does our normal muscular system resemble that of 
monkeys, that until the fifteenth century all knowledge of 
human myology was derived from the dissection of these 
animals. 
What importance are we to attach to reversive abnor- 
malities? Are we to consider them as merely chance 
developments, due, as it were, to accidental variations in 
the mould; or are we to regard them as possessing a 
further signification, and meriting the title “‘ reversive?” 
“~~ 
