VIII.] 



THE COMMON FROG. 



115 



fluid be applied to a spot easily reached by one foot, 

 the decapitated frog will apply that foot to the spot. 

 More than this, if that foot be cut off it will move the 

 stump as before, seeking to reach the spot and failing 

 so to do, will then apply the other foot to the irritated 

 locality. 



These, and such experiments, are of course con- 

 clusive, if the common assumption be conceded that 

 the brain is the indispensable nervous instrument of 

 sensation. 



\ 



Fig. 71. — The Brain of Man as seen when a Vertical Longitudinal Section has been 

 made through its middle. Av, arbor vitae of the cerebellum; c, cerebrum; cc, 

 corpus callosum ; ci^,* corpora quadrigemina ;y, fornix (between the fornix and the 

 coi-pus callosum is the septum lucidum) ; m, medulla oblongata ; 7Ha, corpus 

 mammillare ; on, optic nerve ; //, pineal gland ; //, pituitary body ; pv, pons 

 Varolii ; s, soft or middle commissure. 



It is possible, however, that the faculty of sensa- 

 tion may be subserved by the spinal cord without the 

 brain, and if so, all these much vaunted experiments 

 are valueless as regards the truth of pure reflex 

 action, not but that they are of extreme interest, 

 as showing what may be done in lower animals 

 without the intervention of any brain action what- 

 ever. 



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