ON THE MAMMALIAN NERVOUS SYSTEM. 279 



method the localisation and quantitative estimation of either centripetal or efferent 

 impulses issuing from nerve centres in functional activity, and, in addition, we first 

 employed it for the determination of the localisation of paths or channels of nerve 

 function, particularly in the spinal cord. After this preliminary statement, which has 

 been rendered necessary by the publications referred to, we will refer to the results 

 which were obtained by FLETSCHL and BECK respectively, although, as we said just 

 now, these results are, we consider, for the reasons we discuss on p. 29(5, not to be 

 immediately accepted. FLEISCHL (loc. cit.) connected, by means of non-polarisable 

 electrodes, two symmetrical points on the surfaces of the cerebral hemispheres with 

 the galvanometer, and found that in the resting condition there was little or no 

 electrical difference. If, however, a sensory end organ, whose corresponding area of 

 the cortex was thus connected, were excited, the effect produced was an electrical 

 difference as recorded by the deflection of the galvanometer. This effect he especially 

 obtained when the visual centre discovered by MUNK was connected with the 

 galvanometer and the eye illuminated, whereas little or no difference followed ex- 

 citation of cutaneous nerve endings. Finally, he found that profound narcosis with 

 chloroform or ether abolished this effect, and that special precautions must be taken 

 against cooling of the preparations. 



BECK (loc. cit.) removed the brain, spinal cord, and sciatic nerve of the frog en 

 bloc and placed the preparation on a glass plate ; he then applied non-polarisable 

 electrodes made of kaolin and 0'6 per cent, salt solution to the longitudinal surface of 

 the spinal cord and connected them with a Hermann's galvanometer. He found 

 that there was constantly an electrical difference of such a nature that the centripetal, 

 i.e., proximal parts of the nervous system were always electro-negative to centrifugal 

 or distal parts. If then the sciatic nerve were excited this primary difference was 

 increased, provided the galvanometer electrodes were placed above the lumbar en- 

 largement. If, on the other hand, the sciatic nerve were excited while one of the 

 non-polarisable or lead ing-off electrodes were placed on the lumbar enlargement, there 

 was observed a negative variation of the primary difference. In another series of 

 experiments on Dogs and Rabbits he connected two points of the surface on one 

 hemisphere with the galvanometer, and found that there were more or less regular 

 swaying movements of the needle, and which he regarded as "action currents." 

 Excitation of the retina caused the visual centre of MUNK to become negative to the 

 rest of the hemisphere. 



DANILEWSKY* has quite recently published the results of five experiments which 

 he performed in 1876, and in which he found that when non-polarisable electrodes 

 were connected with the cerebral hemispheres (whether superficially or deeply) and 

 with a sensitive du Bois-Reymond galvanometer "negative variations of the resting 

 difference were observable as consequences of various modes of sensory stimulation. 

 The portion of the hemisphere from which these effects were obtained was the 



* ' Centralblatt fiir Physiologie,' April, 1891, p. 1. 



