312 MESSRS. F. GOTCH AND V. HORSLEY 



The comparison shows that the amount of the resting difference in the anaesthetised 

 animal is larger when the cerebral connections are intact. 



This conclusion is supported by direct experimentation upon the influence of 

 severance. Thus in an anaesthetised animal (Cat) the cord was exposed and divided 

 at the level of the 4th lumbar vertebra and the central end ligatured. It was then 

 suspended in the usual way and the electrodes attached to the cross section and the 

 longitudinal surface. The resting difference amounted to "044 Daniell, whereas, when 

 the cord was severed higher up at the 7th dorsal vertebra, a notable fall to '037 

 Daniell occurred. 



In another experiment (Cat, 315) the cord was divided at the 13th dorsal vertebra 

 and similarly prepared. Its central end was then connected with the galvanometer 

 electrodes as above. The amount of the difference between the surface on the central 

 side of the cross section and the cross section itself amounted to '04 Daniell. A 

 hemisection of the cord at the 8th dorsal vertebra was now made and the difference fell 

 rapidly to '38 Daniell, the rapid fall then ceased, but a slow fall continued for some 

 time. 



These experiments suggest that severance in an anaesthetised animal of the cord 

 from the brain causes a direct diminution in the amount of the resting difference 

 below the point of severance, whether by the interference with the circulation which 

 such severance may imply, or by this aided by the interruption in the path which 

 joins at any rate some of the (pyramidal) fibres with the cells with which they are in 

 direct connection and which govern their nutrition. As will be seen later there is no 

 evidence of a similar diminution being produced when the cross sections are made 

 upon a portion of cord already severed from the brain by an interruption higher up. 

 Hence the inference that the fall is correlated with the interruption (in the pyramidal 

 fibres ?) is strengthened. 



Finally the region of cord investigated has some relation with the amount of the 

 resting difference. This is shown in Appendix B, III., in which observations made in 

 the dorsal region are separated from those in the lumbar region. 



The average of the dorsal region = "029 ; highest '043, lowest '014. 



The average of the lumbar region = '033 ; highest '04, lowest '028. 



Although the average seems to show that the difference in the dorsal cord is 

 less than that in the lumbar, yet an examination of the highest and lowest limits 

 suggests that the preponderance, in the latter case, is due to the fact that in the 

 dorsal cord several very low readings were obtained. (See Table (2) ; Appendix B, 

 III., Cats 194, 289, 349.) 



We have endeavoured to get some notion of the relations of the different regions by 

 exposing in an anaesthetised animal (Cat 36) the whole cord. This was then divided 

 into three equal lengths, comprising the cervical, dorsal, and lumbar regions respec- 

 tively, and the three placed in a warm moist chamber for examination. 



