APPABATUS OF MOTION IN GENERAL. 129 



all the muscles. Injury done to the corpus striatum renders 

 the muscular movements confused and uncertain ; the power 

 of retiring is lost, the movements being always in advance : 

 an injury done to the cerebellum (in birds) seems, on the 

 contrary, to disable the animal from advancing ; its move- 

 ments are constantly backwards. 



By dividing vertically in a living animal one hemisphere 

 of the cerebellum, or one side of the pons, the animal moves 

 incessantly round and round towards the injured side. The 

 vital point of the encephalon seems to be close to the origin 

 of the pneumogastric nerves. The cerebellum and the ad- 

 joining parts of the brain seem to regulate the movements of 

 locomotion. 



The movements which, though obeying the will, yet take 

 place independently of its influence, seem to be derived, then, 

 from the influence of the spinal marrow. The respiratory 

 movements, for example, go on after the brain has lost its in- 

 fluence over the respiratory muscles. 



256. Influence of the Ganglionic System. The mus- 

 cular fibres, which are completely independent of the will, 

 receive their nervous influence from this system. 



257. Thus it would seem that, whilst volition proceeds 

 from the brain, the regulation of the movements proceeds 

 from the cerebellum ; whilst, in respect of those muscular 

 actions which are independent of the brain, the principle of 

 action seems to reside in the spinal marrow and ganglionary 

 system. 



258. Duration and Force of the Muscular Con- 

 tractions. The contraction of the muscular fibres is a phe- 

 nomenon essentially intermittent; they relax and contract 

 alternately. Even the heart does this ; but the voluntary 

 muscles require a much longer interval of repose ; a lassitude 

 comes on at last, rendering all further action impossible. 



Muscular fatigue varies much in different individuals ; so 

 also does the strength of contraction displayed. In passion 

 and in a maniacal state it is prodigious. The development 

 of the muscular system is best seen in the athlete. 



Of the Apparatus of Motion in General. 



259. The function we have now to consider is chiefly 

 mechanical; it respects the various movements of animal 

 bodies. 



K 



