Collaboration with Marsh 71 



of liis conclusions, and the credit of the final result is to 

 be shared at least equally between Marsh and Huxley. 

 The final result was a demonstrative proof of the pos- 

 sible course of evolution of the horse, given in a lecture 

 deliv^ered by Huxley in New York on Sept. 22, 1876, 

 and illustrated by drawings from specimens in Marsh's 

 collection. The matter of the lecture has become so 

 important a part of all descriptive writing on evolution, 

 and the treatment is so characteristic of Huxlej^'s bril- 

 liant exposition, that it is worth while to make some 

 rather long quotations from it. The lecture was pub- 

 lished in the New York papers, and afterwards with 

 other matter formed a volume of American Addresses, 

 published by Macmillan, in lyondon. 



" In most quadrupeds, as iu ourselves, the forearm contaius 

 distinct boues called the radius aud the ulua. The correspond- 

 ing region in the horse seems at first to possess but one bone. 

 Careful observation, however, enables us to distinguish in this 

 bone a part which clearly answers to the upper end of the ulna. 

 This is closely united with the chief mass of the bone which 

 represents the radius, and runs out into a slender shaft which 

 may be traced for some distance downwards on the back of the 

 radius, and then in most cases thins out and vanishes. It takes 

 still more trouble to make sure of what is nevertheless the fact, 

 that a small part of the lower end of the bone of the horse's 

 forearm, which is only distinct in a very young foal, is really 

 the lower extremity of the ulna. 



"What is commonly called the knee of a horse is its wrist. 

 The ' cannon bone ' answers to the middle bone of the five 

 metacarpal bones which support the palm of the hand in our- 

 selves. The 'pastern,' 'coronarj,' and 'coffin ' bones of vet- 

 erinarians answer to the joints of our middle fingers, while the 

 hoof is simply a greatly enlarged and thickened nail. But, if 

 what lies below the horse's ' knee ' thus corresponds to the 

 middle finger in ourselves, what has become of the four other 

 fingers or digits? We find in the places of the second and 

 fourth digits only two slender splint-like bones, about two- 



