ON THE MAMMALIAN NERVOUS SYSTEM. 



357 



whilst the cord effect evoked by the right cortex was increased to 134 scale, an effect 

 was also evoked by excitation of the left cortex, though it amounted to only 15 scale. 

 The cord was next divided longitudinally and the electrical change observed on 

 the two sides with the following result, it being remembered that the right half of the 

 cord had been interrupted by the previous hemisection. 



It is clear from this that in the half of the cord (left) which offered an 

 uninterrupted channel, the excitation of the cortex of the opposite side evoked large 

 results, whilst the excitation of the cortex of the same side side evoked no results 

 until a considerable intensity of stimulus was used and a bilateral fit produced. On 

 microscopical investigation the lesion in the cord showed that the whole of the right 

 half of the cord was destroyed, and the anterior third of the left posterior column, and 

 the left posterior median. The descending degeneration, therefore, affected the right 

 pyramidal tract in the lateral column only. The ascending degeneration affected both 

 postero-median columns and the right cerebellar and antero-lateral tracts. 



It should be mentioned that SCHIFF S observations on hemisections made just 

 before excitation of the cortex show that the same relationships prevail as regards 

 muscular movements. 



III. Excitation of Corona Radiata. Electrical effect observed in each Half of Split 



Cord. 



The genera] electrical phenomena observed after excitation of the corona radiata, 

 and especially as contrasted with those elicited by exciting the cortex are described 

 in Chapter VI., but in attempting to still further elucidate the subject of bilaterality 

 we arranged a third variety of experiment, originally designed for the graphic method 

 by FRA.NCK and PITRES and others, viz., the investigation of the bilateral phenomenon 

 noted after excision of the cortex, and consequent upon excitation of the subjacent 

 corona radiata. 



We have considered, on p. 338, the errors it involves, and have always endeavoured 

 to minimise them as far as possible just as in the case of the cortex. Although 

 the results are thus of necessity only to be accepted with reservations on the 

 points already mentioned, which we must again briefly notice, nevertheless they do 

 afford some very suggestive deductions. 



