iiu SPLANCHNIC FUNCTIONS or THE BRAIN. [BOOKIH. 



conspicuous tie between the posterior corpora quadrigemina and 

 the parts of the nervous system behind them, does not appear to 

 have any marked effect in producing incoordination. 



In fine, beyond the broad facts on which we dwelt in a 

 previous section, namely, that we maintain our equilibrium and 

 carry out complex movements involving often several parts of our 

 body, through what we call coordination, that afferent impulses 

 supply important factors of this coordination, and that the 

 cerebellum, through the vestibular nerves in part at all events, 

 together with other portions of the middle brain, are in some way 

 its chief instruments, we as yet know very little. We have 

 certainly no adequate knowledge as to how either pair of corpora 

 quadrigemina exactly intervene in the matter, or, indeed, as to 

 what other parts they play in the general work of the brain. 



With regard to other tracts of fibres or areas of grey matter 

 we have nothing to say, except as regards those which are more 

 or less immediately connected with certain of the cranial nerves, 

 such for instance as the nerves for movements of the eyes, and 

 these it will be best to consider when we have to deal with the 

 nerves themselves. 



689. Besides the somatic functions which in previous 

 discussions we have chiefly had in view, the brain as a whole 

 undoubtedly carries out splanchnic functions; concerning these, 

 however, we must be very brief. 



Of the respiratory and vaso-motor functions of the bulb we 

 have already treated in their appropriate places, and we have 

 referred ( 535) to the experimental evidence that a lesion of the 

 corpus striatum, or of the front part of the optic thalamus has a 

 remarkable influence on the development of heat in the body. 

 We have further seen that the higher parts of the brain, acting 

 through the bulb, exercise powerful influences on respiration, on 

 the vaso-motor system, and on the beat of the heart. Daily 

 experience affords abundant instances of actions such as these, 

 as well as of the influence of the brain on other organic functions. 

 We can bring our will to bear on the mechanism of micturition 

 ( 430) which is almost wholly, and on the mechanism of 

 defaecation ( 275) which is largely, splanchnic in nature. These 

 movements, however, are not skilled movements ; and as we 

 explained in dealing with them, the action of the brain as regards 

 them seems limited to augmenting or inhibiting the activity of 

 spinal centres. We should therefore hardly expect them to be 

 specially represented in the cortical motor region. But emotions 

 have a much wider and more powerful influence over the splanchnic 

 functions than has the will, and have the power of affecting the 

 work of certain organs, for instance the heart and secreting glands, 

 which the will is unable to touch. And since we have every 

 reason to believe that the cortex is closely associated with the 

 emotions, we may naturally infer that elements of the cortex 



