Reflex Electrical Effects in Mixed Nerve, <Jr. 353 



and consequently the progression is undisturbed by the modification 

 of the directional differences for the same salt, which are relatively so 

 much more important in the case of the thermal constants. 



The net effect of the replacement of one metal by another has, how- 

 ever, been shown to be clearly demonstrated by the progression of the 

 coefficients of the cubical expansion and their increments. 

 The final conclusion of the investigation, therefore, is that : 

 The thermal deformation constants of the crystals of the normal sulphates 

 of potassium, rubidium, and ccesium exhibit variations which, in common with 

 the morphological, optical, and other physical properties previously investigated,, 

 follow the order of progression of the atomic weights of the alkali metals which 

 the salts contain. 



" On the Eeflex Electrical Effects in Mixed Nerve and in tbe 

 Anterior and Posterior Boots." By Miss S. C. M. SOWTCW, 

 Communicated by A. D. WALLEK, M.D., F.RS. Eeceived 

 December 12, 1898, Eead February 16, 1899. 



The following experiments were made during the months of May, 

 June, and July, 1897, in the Physiological Laboratory of Leipzig, 

 under the guidance of Professors Hering and v. Frey, to test whether 

 in the frog, reflex electrical changes could be demonstrated at the 

 central end 



I. Of a mixed nerve. 

 II. Of anterior roots alone. 

 III. Of posterior roots alone. 



As regards the first two heads, the end in view was simply the actual 

 verification of an extremely probable phenomenon, preparatory to an 

 examination of the third head, viz., reflex electrical effects propagated 

 down the posterior roots, which, in 1891,* were pointed out by Gotch 

 and Horsley, and offered as proof of the passage of centrifugal nerve 

 impulses in normally afferent nerve channels. The results obtained in 

 the present experiments being somewhat difficult to interpret, the notes 

 were laid aside until opportunity should offer for carrying the investi- 

 gation further. Professor Bernstein having, however, quite recently! 

 discussed the question of the reflex negative variation of the nerve 

 current, the moment seemed opportune for submitting these results 

 as they stand to the attention of those interested in the subject. 



The galvanometer used was on the lines of Thomson's reflecting 

 instrument, with modifications by Carpentier. The leading-off 

 electrodes had finely pointed camel's hair brushes inserted in the plug 



* ' Phil. Trans.,' B, vol. 182. 



f 'Pfliiger's Arclriv,' TO!. 73, p. 374, 1808. 



