888 REPORT— 1893. 



reduced to a minimum, and when estimated proportionally to the size of the body 

 it is believed to be considerably less than that requisite for the corresponding act 

 in quadrupeds. 



The anatomical changes effected in the extremity of the upper limb are 

 equally radical, but of a totally different character and scope. Here we have to 

 contemplate the transformation of the same homologous parts into an apparatus 

 for performing a series of prehensile actions of the most intricate character, but 

 among which neither locomotion nor support of the body forms any part whatever. 

 This apparatus is the human hand, the most complete and perfect mechanical 

 organ nature has yet produced. The fingers have become highly developed, and 

 can be opposed singly or in groups to the thumb, so as to form a "hook, a clasp, or 

 a pair of pincers ; and the palm can be made into a cup-shaped hollow, capable of 

 grasping a sphere. Nor is there any limit to the direction in which many of these 

 manipulations can be performed without any movement of the rest of the body. 

 For example, a pencil held by the thumb aiid the two forefingers, as in the act of 

 writing, can be placed in all the directions of space by a mere act of volition. 



The position of such a perfect piece of mechanism, at the extremity of a 

 movable arm attached to the upper part of the trunk, gives to man a superiority 

 in attack and defence over all other animals, on the same principle as a soldier 

 finds it advantageous to fight from higher ground. Moreover, he possesses the 

 power to perform a variety of quick movements, and to assume attitudes and posi- 

 tions eminently adapted for the exercise of that manipulative skill with which he 

 counteracts the supeiior brute force of many of his antagonists. He can readily 

 balance his body on one or both legs, can turn on his heels as if they were pivots, 

 and can prostrate himself comfortably in the prone or supine positions. As the 

 centre of gravity of the whole body is nearly in line with the spinal axis, stable 

 equilibrium is easily maintained by the lumbar muscles. Altogether we have in 

 his physical constitution a combination of structures and functions sufficiently 

 unique in its tout-eyxsemble to place man in a category by himself. But at the 

 same time we must not forget that all his morphological peculiarities have been 

 brought about without the destruction of any of the primarj' and typical homo- 

 logies common to all the higher vertebrates. 



Turning now to the brain, the undoubted organ of the mind, we find, in its 

 intellectual and psychical manifestations, a class of phenomena which gives to man's 

 life-functions their most remarkable character. However difficult it may be for our 

 limited understanding to comprehend the nature of conscious sensation, we are 

 forced to the conclusion that the act invariably takes place through the instrument- 

 ality of a few nerve-cells, whose functional activity requires to be renovated in 

 precisely the same manner as the muscular force expended in walking. The aggre- 

 gation of such cells into ganglia and nerves, by means of which refiex action, 

 consciousness, and a variety of psychical phenomena take place, is found to per- 

 meate, in a greater or less degree, the whole of the organic world. In the higher 

 vertebrates the seat of these manifestations is almost exclusively confined to an 

 enormous collection of brain substance placed at the upper end of the vertebral 

 column, and encased in a complete osseous covering called the skull. We learn 

 from numerous experimental researches, carried out by physiologists in recent years, 

 that the brain is a dual organ, consisting of a double series of distinct ganglia and 

 connected to some extent by a complex system of nervous tissues, not only with 

 each other, but with the central seat of consciousness and vohtion. But the diffi- 

 culty of determining the natui-e of its functions, and the modus operandi of its 

 psychological manifestations, is so great that I must pass over this part of the sub- 

 ject very hghtly indeed. The conditions of ordinary reflex action require that a 

 group of muscles, by means of which a particular bodily movement is effected, 

 shall be connected with its co-ordinating ganglion by an afferent and an efferent 

 system of nerves. Impressions from without are conveyed by the former, or sen- 

 sory nerves, to the central ganglion, from which an impulse is retransmitted by the 

 motor nerves, and sets in operation the muscular force for producing the required 

 movement. But this efferent message is, in many cases, absolutely controlled by 

 volition ; and not only can it prevent the muscular action from taking place, but it 



