810 SPLANCHNIC FUNCTIONS OF THE BRAIN. [Bookiii. 



remembering that a loud sound will often cause a person to 

 reel, further admit that purely auditory impulses, as distinct 

 from what we have called ampullar impulses, may take part in 

 the general coordination of bodily movements and in the main- 

 tenance of equilibrium, as they certainly do in the special coor- 

 dination of laryngeal movements, still we are not much nearer 

 an understanding of the matter. We may add that section of 

 the lateral fillet, which appears as a 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 rlne, beyond the broad facts on which we dwelt in a pre- 

 vious 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. 



§ 514. 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 (§ 429) 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 (§ 348) which is almost wholly, 

 and on the mechanism of defecation (§ 225) which is largely, 

 splanchnic in nature. These movements, however, are not 

 skilled movements ; and as we explained in dealing with them, 



