1884.1 
The Significance of Human Anomalies. 
67 . 
the arm-pit, on the back, &c. The skin-muscles are well 
developed in those of the Mammalia which have loose skins, 
as, for example, the hedgehog, porcupine, and porpoise. In 
the hedgehog, when the skin-muscles contract, the animal 
becomes rolled up as in a bag of muscles. The sportive 
gambols of a school of porpoises are effected by an abundant 
supply of these skin-muscles ; in the horse the skin-muscle 
is called the panniculus carnosus, and everyone who has seen 
a horse twitching its skin to get rid of troublesome flies will 
easily understand how serviceable it is to that animal. 
In all human beings there is a small muscle going from a 
hooked process ( coracoid ) on the upper end of the shoulder- 
blade to the inner side of the arm-bone, about the junction 
of its upper and middle third. Sometimes this muscle is 
continued down to the lower end of the arm-bone ; or, 
again, it may be quite short, and attached to the bag of 
fibrous tissue covering the shoulder-joint. On referring to 
the anatomy of the lower animals it is found that both these 
varieties exist normally, but in a much more highly deve- 
loped state ; they are especially well seen in animals which 
use their fore-limbs for digging, climbing, or swimming. In 
them the muscle is of large size, and reaches to the inner 
edge of the lower extremity of the arm-bone ; in man, when 
it reaches thus far, it is only rudimentary, and of no use. 
Another muscle which I have seen in about 3 per cent of 
human subjects is a small one which goes from the breast- 
bone to the upper end of the shoulder-blade. This muscle 
is well developed in animals which have no collar-bones ; it 
reaches its highest development in the horse, pig, hippo- 
potamus, and elephant. It is also seen in the Guinea-pig, 
Norway rat, and wombat. It is quite rudimentary when it 
exists in man, and serves no useful purpose. 
In man, near the elbow-joint, and lying close together, are 
two muscles going from the upper to the lower arm ; one in 
front ( brachialis anticus ), which helps to bend the elbow, and 
the other to the outer side ( supinator longus ), which supinates 
or twists the fore-arm outward. As a rule these muscles are 
quite distinct, though they lie side by side; but in about 
1 per cent of cases they are joined together by muscular 
fibres. This is the normal arrangement in apes and mon- 
keys, the union of these two muscles aiding them greatly 
in twisting their bodies when hanging by their fore-limbs to 
the branches of trees. Again, in apes, the muscle forming 
the posterior fold of the arm-pit is always prolonged down 
to the prominence on the back of the elbow. In the long- 
armed apes this muscle is especially well developed, and 
