ON THE MAMMALIAN ^ERVOCJS SYSTEM. 345 



FRANCOIS FRANCK and PITRES* found that in the Dog, after division of the corpus 

 callosum, the anterior and middle commissures, or even the pons, " les rdactions 

 bilaterales " persisted (? tonus only). 



GuKYt also found (see No. 4) bilaterality of movement after dividing all parts in 

 the middle line to the mesencephalon, in the Rabbit. 



HOESLEYJ showed that in the Dog after division of the corpus callosura and com- 

 missures, as described by FRANCK and PITRES, although bilateral movements could 

 be obtained upon excitation of one hemisphere, yet the movements were not the same 

 in character on the two sides ; the true cortical effect of tonus followed by clonus 

 being only obtainable in the side opposite the excitation, whilst the effect on the same 

 side was only a feeble tonus (vide also LEWASCHEW) and often absent. 



3. Excitation Experiments on the Cortex combined with Excision of the Opposite 



"Motor" Area. 



FRANCK and PITRES observed in the Dog the bilateral movements to persist 

 (? tonus only on the same side) even after the opposite motor area had been removed 

 (" centres corticaux opposes au centre excite "), and EXNER|| also in the Kabbit noted 

 the occurrence of bilateral movements if one hemisphere were excited, even when the 

 whole or major part of the opposite one had been excised. 



HORSLEYH found the same in the Dog, but noted that while the limbs opposite (i.e., 

 corresponding) to the side excited developed the usual combination of tonus followed by 

 clonus, the limbs on the same side exhibited only tonus. Further, that as in Nos. 1 

 and 2 the complete (tonic plus clonic) discharge from the cortex of one hemisphere 

 could be obtained by adequate excitation without any bilatei'al movement whatever. 



He also found the same to be true when the excitable region of one hemisphere 

 was ablated and absinthe injected into a vein. In the resulting epileptic convulsion 

 only tonus was noticeable in the limbs corresponding to the seat of ablation, whereas 

 the typical tonus plus clonus was exceedingly marked in the limbs opposite the sound 

 hemisphere. This differentiation was often very precise, i.e., the tonus on the side of 

 the sound cortex was very weak, even in the Cat. 



In the Monkey the tonus mentioned was extremely slight, and possibly in Man is 

 absent (<JBRE) under these circumstances. 



* Loc. cit. 



t ECKHAKU'S ' Beitrage,' vol. 7, p. 179, 1876. 

 J ' Brown Lectures and Reports.' 



See for full discussion FKA^OIS FBANCK : ' Fonctions Motrices du Cerveau,' 1887, p. 59. 

 || Loc. cit. 



Tf ' Brown Lectures ' since 1885 ; also, ' Reports of the Brown Institution,' 

 MDCCCXCI. B, 2 Y 



