In the bear, the length of the radius approaches closely to that of the humerus; the index is about 90. In the skeleton of a bear in the anatomical museum of the École des Beaux-Arts, the humerus is 33 centimetres in length, and the radius 30 centimetres.
In the cat, the radius is very little shorter than the humerus. In the dog they are equal. The antibrachial index of the latter is, accordingly, 100.
In the horse, the radius is longer than the humerus; the index is therefore above 100. Thus, in the skeleton of the horse which we have in the museum of the École des Beaux-Arts, the index is 113--length of humerus, 29 centimetres; length of radius, 33 centimetres. In other skeletons which we have measured we found: in one, 108--humerus, 34 centimetres; radius, 37 centimetres; in another, 116--humerus, 25 centimetres; radius, 29 centimetres.
The metacarpal bone undergoes, relatively to the humerus, a proportional elongation, analogous to that of the forearm.
In man, the length of the metacarpus is contained about 5-1/2 times in that of the humerus; in the bear, it is contained 4 times; in the dog, 2-1/2 times; in the horse, 1-1/3 times only.
It is well known that the proportions vary according to race, and that what we have here given are but the general indications.
The knowledge of human arthrology which we presume the reader to have previously acquired makes it unnecessary for us to enter into numerous details regarding the configuration of the articular osseous surfaces and the disposition of the fibrous bands that retain them in position. Accordingly, in the description which follows, and also in that of the articulations of the posterior limbs, we shall occupy ourselves but very briefly with the details above referred to, so as to devote ourselves especially to the indication of the movements--that is to say, of that which, while easily comprehended on recollection of former studies, presents the greatest interest from the artistic standpoint in these studies in comparative anatomy.
=The Scapulo-Humeral Articulation.=--The head of the humerus and the glenoid cavity of the scapula being in contact, the two bones are bound together by a rather loose articular capsule, which is strengthened by the muscles of this region which fulfil the function of active ligaments.