886 REPORT— 1893. 



the principles by whicb it could be effected became important factors in natural 

 selection. I need not here dwell on the various methods by ■which this has been 

 accomplished in the lower forms of hfe, but proceed at once to point out that in 

 the higher vertebrates the problem resolved itself into the well-known mechanism 

 of four movable limbs, capable of supporting and transporting the animal. As 

 these quadrupedal animals became more highly differentiated, in virtue of the 

 necessities of the struggle for life and the different and ever- varying conditions of 

 their surroundings, it followed that the limbs became also modified so as to make 

 them suitable, not only for locomotion in various circumstances, but also useful 

 to the animal economy in other ways. Hence they were subjected to an endless 

 variety of secondary influences, which finally adapted them for such diverse pur- 

 poses as swimming, flying, climbing, grasping, &c. The anterior limbs, owing to 

 their proximity to the head, were more frequently selected for such transformations 

 as may be seen, for instance, in the wings of a bird. But whatever modifications 

 tha fore limbs may have undergone, no animal, with the exception of man, has 

 ever succeeded in divesting them altogether of their primary function. This 

 exceptional result was due to the erect position, which necessitated a complete 

 division of labour as regards the functions of the limbs — the two anterior being 

 entirely restricted to manipulative and prehensile purposes, and the two posterior 

 exclusively devoted to locomotion. Coincident with this notable specialisation of 

 their function a new field for advancement was opened up to man, in which intel- 

 ligence and mechanical skill became the leading factors in his further development. 



Man is thus distinguished from all other animals by the fact ihat, in the- 

 normal position of walking or running, he carries his body upright, i.e., with 

 the axis of the vertebral column perpendicular, instead of horizontal or oblique. 

 In this position all its parts are so arranged as to require a minimum amount of 

 exertion in the performance of their functions. If any of the other higher ver- 

 tebrates should ever assume an erect attitude it can only be maintained tempo- 

 rarily, and its maintenance involves an additional expenditure of force. In a 

 certain sense a bird may be looked upon as a biped, but there is this distinction 

 to be drawn between it and man, viz., that the former has not only its body 

 balanced obliquely on its two legs, but also its fore limbs converted into special 

 organs for motion in the air. The anthropoid apes hold an intermediate posi- 

 tion, and so carry their body in a semi-erect attitude. But this shortcoming in 

 reaching the perfectly upright position, however slight it may be in some of these 

 animals, represents a wide gap which can only be fully appreciated by a careful 

 study of the physiological and psychological phenomena manifested in their respec- 

 tive life-functions. 



Everyone acquainted with the ordinary operations of daily life knows how 

 much labour can be saved by attention to the mere mechanical principles in- 

 volved in their execution. In carrying a heavy load the great object is to adjust 

 it so that its centre of gravity comes as nearly as possible to the vertical axis of 

 the body, as otherwise force is uselessly expended in the effort to keep the entire- 

 moving mass in stable equilibrium — a principle well exemplified by the Italian 

 peasant girl when she poises her basket of oranges on her head. Once upon a 

 time a powerful waterman, accustomed to use buckets double the size of those 

 of his fellow-watermen, had the misfortune to have one of them broken. As he^ 

 could not, then and there, get another bucket to match the remaining one, and 

 wishing to make the best possible use of the appliances at hand, he replaced 

 the broken vessel by one half its size. He then filled both with water and 

 attempted to carry them, as formerly, attached to a yoke, one on each side of him. 

 But to his astonishment this arrangement would not work. The yoke became un- 

 even, and the effort to keep it balanced on his shoulders was so troiiblesome that 

 he could not proceed. This emergency led to serious reflection, but, after some 

 experimental trials, he ascertained that, by merely making the arm of the yoke 

 on which the small bucket was suspended double the length of the other, he could' 

 carry both buckets without inconvenience. 



But let me take one other illustration. Suppose that two burglars have con- 

 cocted a plan to rob a richly-stored mansion by getting access to its rooms throughi 



