210 ANIMAL PHYSIOLOGY. 



through, a sensorium commune extending throughout the 

 nervous system; but the loss of all sensation in parts whose 

 nervous communication with the brain has been severed puts 

 an end to that theory. At the present day, it is customary 

 to say that the mind refers impressions received at the brain 

 to the extremities of the nerves by which they have been con- 

 ducted. But it is perfectly certain that there is no separate 

 nervous communication between the brain and each point of 

 the surface of the body in which sensations can be dis- 

 tinguished. The question is of the utmost interest psycho- 

 logically, but is still unsettled. Personally, I believe that 

 the only tenable theory yet put forward is that which I have 

 elsewhere broached, viz., that while consciousness is dependent 

 on the encephalon, the sensorium extends thence, so far as 

 there is, at any moment, unbroken continuity of nerves in 

 the active or impressed condition. 



154. It is frequently supposed that different parts of the 

 hemispheres are connected with different faculties of the 

 mind; and the opinion that the frontal, parietal, and occipital 

 regions are devoted respectively to the intellectual powers, 

 moral faculties and appetites, or in some other way differ 

 in function, is not confined to the believers in the system 

 founded by Gall, and commonly known as phrenology. But 

 there is no foundation for any such supposition. On the 

 contrary, the evidence points to an opposite conclusion. 

 Serious damage to the hemispheres, of a limited description, 

 often occurs without loss of life, and such cases may occur 

 without any apparent interference with intellectual functions. 

 A tumour may press on some particular part of a hemisphere 

 without producing any disturbance, and bodies have pene- 

 trated the brain, and portions of brain protruding from 

 wounds have been removed by surgeons, without any obvious 

 impairment of the mental faculties. Not only, so, but the 

 kind of disturbance which is liable to occur from such injuries 

 does not vary according to the site of lesion, so as to affect, 

 in one instance, the faculties of perception, in another the 

 disposition, and in a third the powers of volition, as might 

 be expected, were phrenological theories true. 



In recent years a little colour has seemed to be given to 

 the theory of separate organs in the cerebral hemispheres, by 



