FUNCTIONS OF THE BRAIN 981 



orbicularis oculi as a test, Ziehen has come to the conclusion that 

 in the anthropoid apes and in man this centre has been pushed 

 forward by the encroachment of the centres behind it, and especially 

 of the visual centre, the arm centre, and the speech centre, which 

 have undergone a great functional development. 



Acquisition of Co-ordination of Voluntary Movements. The co-ordina- 

 tion of movements has already been alluded to in connection with the 

 spinal reflexes. No fundamental distinction can be drawn between the 

 co-ordination of reflex and of voluntary movements, but the conscious 

 and often long-continued efforts necessary to acquire mastery over the 

 latter lends to their co-ordination a special interest. The new-born child 

 brings with it into the world a certain endowment of co-ordinative 

 powers; it has inherited, for example, from a long line of mammalian 

 ancestors the power of performing those movements of the cheeks, lips, 

 and tongue, on which sucking depends; perhaps from a long, though 

 somewhat shadowy, race of arboreal ancestors the power of clinging 

 with hands and feet, and thus suspending itself in the air. Many move- 

 ments, such as walking and the co-ordinated muscular contractions 

 involved in standing, and even in sitting, which, once acquired, appear 

 so natural and spontaneous, have to be learnt by painful effort in the 

 hard school of (infantile) experience, and this despite the fact that in 

 these movements the voluntary co-ordination mechanism makes use to 

 a great extent of a motor machinery already existing in the cord and 

 capable of discharging well co-ordinated reflexes.* In addition to such 

 fundamental movements, most people consciously learn, and are 

 willing to confess that they have learnt, to execute a considerable 

 number of co-ordinated movements with the arms, and especially with 

 the fingers. Some part even of the extreme dexterity of jaws, tongue, 

 and teeth displayed by a hungry school-boy, in a minor degree, perhaps, 

 by a hungry mouse, is the result of the much practice, entailing at first 

 some conscious effort, which maketh perfect. The exquisite co-ordina- 

 tion of the muscles of the eyeball, which we shall afterwards have to 

 speak of, and the no less wonderful balance of effort and resistance, of 

 power put forth and work to be done, of which we have already had 

 glimpses in studying the mechanism of voice and speech, become to a 

 great extent the common property of all fully-developed persons. But 

 the technique of the finished singer or musician, of the swordsman or 

 acrobat, and even the operative skill of the surgeon, are in large part the 

 outcome of a special and acquired agility of mind or bod-, in virtue of 

 which highly-complicated co-ordinated movements are promptly deter- 

 mined on and immediately executed. 



With such special and elaborate movements it is impossible to occupy 

 ourselves in a book like this. Their number may be almost indefinitely 



* The question, how much is ' learned ' in an act such as walking, and 

 how much is already present at birth in the form of a co-ordinated mechanism 

 in the nervous system, is not easy to answer, and indeed the answer may be 

 different for different animals. It has been shown that even the unborn 

 foetus of the cat, when shelled out of the uterus into saline solution without 

 interference with the circulation through the umbilical cord, can be made to 

 execute unmistakable movements of progression under the influence of 

 asphyxia, produced by pressure upon the cord. It may also execute such 

 movements spontaneously. Graham Brown, to whom we owe these facts, 

 concludes that the co-ordination of the mechanism concerned in walking is 

 already developed during intra-uterjne life, and is not ' learned ' after birth. 



