THE GREAT CHIMPANZEE. 415 



development of the processes, ridges and crests, and also by the general proportions of 

 the bones themselves, especially those of the limbs, the anatomist judges of the muscular 

 power of the individual to whom a skeleton imder comparison has appertained. 



The influence of muscular actions in the growth of bone is more strikingly displayed 

 in the change of form which the cranium of the young carnivore or the sternum of the 

 young bird undergoes in the progress to maturity ; not more so, however, than is mani- 

 fested in the progress of the development of the cranium of the Chimpanzee itself, which 

 results in a change of character so great as almost to be called a metamorphosis. 



In some of the races of the domestic dog, the tendency to the development of parietal 

 and occipital cristte is lost, and the cranial dome continues smooth and round from one 

 generation of the smaller spaniel, or dwarf pug, e.g. to another; whilst in the large 

 deer-hound those bony crist^e are as strongly developed as in the wolf. Such modifica- 

 tions however are unaccompanied by any change in the connections, that is, m the dis- 

 position of the sutures of the cranial bones ; they are due chiefly to arrests of develop- 

 ment,— to retention of more or less of the characters of immaturity : even the large 

 proportional size of the brain in the smaller varieties of house-dog is in a great degree 

 due to the rapid acquisition by the cerebral organ of its specific size, agreeably with the 

 general law of its development, but which is attended in the varieties cited by an arrest 

 of the general growth of the body, as well as of the particular developments of the skull 

 in relation to the muscles of the jaws. 



No species of animal has been subject to such decisive experiments, continued through 

 so many generations, as to the influence of diff-erent degrees of exercise of the muscular 

 system, difference in regard to food, association with Man, and the concomitant stimulus 

 to the development of intelligence, as the dog. And no domestic animal manifests so 

 great a range of variety in regard to general size, to the colour and character of the 

 hair, and to the form of the head as it is aff-ected by diff-erent proportions of the cranium 

 and face, and by the intermuscular crests superadded to the cranial parietes. Yet under 

 the extremest mask of variety so superinduced, the naturalist detects in the dental for- 

 mula and in the construction of the cranium the unmistakeable generic and specific 

 characters of the Canis familiaris. This and every other analogy applicable to the pre- 

 sent question justifies the conclusion that the range of variety allotted to the Chim- 

 panzee under the operation of external circumstances favourable to its higher develop- 

 ment would be restricted to diff'erences of size, of colour and other characters of the 

 hair, and of the shape of the head, in so far as this is influenced by the arrest of general 

 growth after the acquisition by the brain of its mature proportions, and by the develop- 

 ment, or otherwise, of processes, crests and ridges for the attachment of muscles. The 

 most 'striking deviations from the form of the human cranium which that part presents 

 in the great Orangs and Chimpanzees result from the latter acknowledged modifiable 

 characters, and might be similarly produced ; but not every deviation from the cranial 

 structure of Man, nor any of the important ones upon which the naturalist relies for 



3 L it 



