ON THE MAMMALIAN NERVOUS SYSTEM. 303 



The special structures investigated fall into three classes 



A. Sciatic nerve. 



B. Posterior root. 



C. Anterior root. 



D. Spinal cord. 



A. SCIATIC NERVE. 

 1. Amount of Difference. 



The resting difference between the cross section and the longitudinal surface of the 

 Mammalian nerve was estimated by r>u BOIS-REYMOND as '026 D. in the case of the 

 Rabbit ;* a much less marked difference, '005 D., was observed by ISRAEL! in the 

 sciatic of the same animal. The amount of the difference in the sciatic nerve was 

 observed in various Mammals by FREDERICQ,J who obtained the following results : 



Cat . . . . -017 to -018 Daniell. 



Dog .... "018 '024 



Rabbit . . '015 "028 



Duck . . . -024 -026 



Horse . . . '004 '007 



Our own results were obtained with the Cat and Monkey. In all cases the sciatic 

 nerve of the anaesthetised animal was exposed in the popliteal space, ligatured, and 

 divided below the ligature. 



The results obtained with 69 sciatic nerves in the Cat are given in Appendix B, L, 

 these are separated into those in which the cord, and thus the nerve, was connected with 

 the brain, and those in which the cord was divided. The average result of both sets is 

 the same, being '0094 Daniell in both. The influence of complete section of the nerve 

 at the sciatic notch was also observed in some cases, and was found not to affect the 

 amount of the difference for the first minute or two. The highest difference ever 

 observed was Cat (70) and Cat (75), when it amounted to '018 Daniell, the lowest 

 was '004. Whilst then the average amount is much lower than that which previous 

 observers above referred to obtained in the Rabbit, the maximum corresponds to that 

 noted by FREDERIOQ in the Cat. 



The results obtained in the case of the Monkey are shown in Appendix B, I. Twelve 



* ' Gesammelte Abhandl.,' vol. 2, p. 250. 



t ISRAEL, ' Archiv f. Anat. u. Physiol.,' 1877 (' Physiol. Abth.,') p. 451. 



J FBEDEEICQ, ' Archiv f. Anat. u. Physiol.,' 1880 (' Physiol. Abth.,') p. 65. 



In all cases where a number in brackets follows the mention of an animal, e.g., Cat (70), it refers 

 to the page in our note ledger. The number of observations is so largo that, for purposes of control and 

 correction, we have been compelled to thus check the record. 



