PROFESSOR HUXLEY'S LECTURES. 287 



ordinarily understand as such, but also asses and their modifications, 

 zebras, etc. The horse is in many ways a most remarkable animal, 

 inasmuch as it presents us with an example of one of the most perfect 

 pieces of machinery in the animal kingdom. In fact, among mammals 

 it cannot be said that there is any locomotive so perfectly adapted to 

 its purposes, doing so much work with so small a quantity of fuel, as 

 this animal the horse. And, as a necessary consequence of any sort 

 of perfection, of mechanical perfection as of others, you find that the 

 horse is a beautiful creature, one of the most beautiful of all land- 

 animals. Look at the perfect balance of its form, and the rhythm 

 and perfection of its action. The locomotive apparatus is, as you are 

 aware, resident in its slender fore and hind limbs ; they are flexible 

 and elastic levers, capable of being moved by very powerful muscles ; 

 and, in order to supply the engines which work these levers with the 

 force which they expend, the horse is provided with a very perfect 

 feeding apparatus, a very perfect digestive apparatus. 



Without attempting to take you very far into the region of osteo- 

 logical detail, I must nevertheless for this question depends upon 

 the comparison of such details trouble you with some points respect- 

 ing the anatomical structure of the horse, and more especially with 

 those which refer to the structure of its fore and hind limbs. But I 

 shall only touch upon those points which are absolutely essential to 

 the inquiry that we have at present put. Heie is the fore-leg of a 

 horse : The bone which is cut across at this point is that which 

 answers to the upper-arm bone in my arm, what you would call the 

 humerus. This bone corresponds with my forearm. What Ave com- 

 monly term the knee of the horse is the wrist ; it answers to the wrist 

 in man. This part of the horse's leg answers to one of the human 

 fingers, and the hoof which covers this extended joint answers to one 

 of my nails. 



You observe that, to all appearance, there is only one bone in the 

 forearm. Nevertheless, at the upper end I can trace two separate 

 portions ; this part of the limb, and the one I am now touching. But 

 as I go farther down it runs at the back part into the general bone, 

 and I cease to be able to trace it" beyond a certain point. This large 

 bone is what is termed the radius, and answers to the bone I am touch- 

 ing in my arm, and this other portion of bone corresponds to what is 

 called the ulna. To all appearance in the forearm of the horse the 

 ulna is rudimentary, and seems to be fused into one bone with the 

 radius. 



It looks thus as if the ulna, running off below, came to an end 

 and it very often happens in works on the anatomy of the horse that 

 vou find these facts are referred to, and a horse is said to have an im- 

 perfect ulna. But a careful examination shows you that the lower 

 extremity of the ulna is not wanting in the horse. If you examine a 

 yery young horse's limb you will find that this portion of the bone I 



