328 Scientific Proceedings^ Royal Dublin Society. 



wlieu it is short, it is erect. With the recumbent humerus, the scapula is 

 erect ; with the erect humerus, the scapula is thrown backwards into an 

 oblique position. Now tliis determines balance in the horse, because the body 

 is mainly suspended by muscles coming from tlie summits of the scapula bones. 

 When the scapula lies far back on the thorax, the body rides forwards and 

 the weiglit is nearly under the supporting power. When, on tlie contrary, 

 tlie scapula is erect and far forward on the thorax, the body necessarily 

 liangs back a long way beliind the supporting power. It will be realized 

 liow badly liandicapped as regards the carriage of the body is the horse 

 with the upright scapula. Nature, therefore, in shortening the humerus, 

 confers on tlie horse the quality of balance and to some extent the attribute 

 of speed. 



I have now to show that there is a variation in the hind limb which 

 affects speed more directly, since tlie hind limbs are the propelling limbs 

 of the body. Just as speed is determined in the fore limbs by tlie short 

 humerus, so it is determined in the hind limbs by the shortness of the femur. 

 The long femur, like the long humerus, is recumbent ; the short femur, like 

 the short humerus, is ei-ect. The criterion of speed in both the limbs is tlie 

 open angle. In the fore limb it is the angle of the elbow ; in the hind limb 

 that of the stifle. 



We recognize the advance that has been made in the perfection of the 

 liorse as regards both speed and balance by the wide variation of these 

 angles. That as regards balance at least, the limit of perfection has not 

 been reached in the horse, will be learnt by studying the skeleton of what 

 1 assume to have been a fast animal, such as the Irish elk, adapted to carry 

 heavy antlers (fig. 9). As may be seen in the specimens in the National 

 Museum, Dublin, and elsewhere, the scapula is relatively very large, and it 

 is thrown back on the thorax by a short erect humerus. That the Irish 

 elk was fast is proved also by the short femur and the very open angle of 

 the stifle. 



Such glimpses as this into the aims and attainments of nature, while 

 exciting wonder and reverence, will make regret the more keen that whole 

 races of the horse have deteriorated under domestication from the type of 

 the natural animal, and that we should allow to pass, as of little consequence, 

 the primitive excellence of the short head and spine, without i-ealizing that 

 under so simple a character lies so much that is beautiful and useful in the 

 horse. 



How do the above-mentioned variations in tlie skeleton of the horse affect 

 " action " ? It will be obvious that true direction of movement is only 

 possible with the primitive arrangement of the limbs in parallel planes, 



