ON THE MAMMALIAN NERVOUS SYSTEM. 383 



they spring ; and it need hardly be pointed out that, whilst minute localisation of 

 representation of movements on the cortex of the Monkey has been clearly demon 

 strated, such perfect differentiation has not been found in the Carnivora. 



We will now pass on to the consideration of the results obtained when the dorsal 

 portion of the experimental tract of the cord is connected with the galvanometer, and 

 the columns excited in the lumbar region, thus evoking impulses which, to produce 

 effects, in ust pass up the cord. 



SECTION 7. ELECTRICAL EXCITATION EFFECTS EVOKED IN THE DORSAL REGION OF 

 THE CORD BY EXCITATION OF THE COLUMNS IN THE LUMBAR REGION. 



In these experiments the cord was divided in two places, as described in the 

 preceding paragraphs ; but, since the electrical effects in the dorsal end of the 

 tract thus isolated were to be investigated, the cord was prepared for several centi 

 metres at the upper dorsal level. At the lower lumbar section the cord was prepared 

 by excision of one centimetre for purposes of excitation. The exciting and galvano- 

 metric arrangements were of the same character as before, their relative disposition 

 being sufficiently indicated in the annexed fig. 14. 



(a.) Typical Experiments. 



We will again first describe the results of an experiment selected as a typical one, 

 and carried out on the spinal cord of the Cat (244), as follows . 



The cord was divided at the 7th dorsal vertebra and prepared for observation as 

 before described : it was then divided at the 2nd lumbar vertebra for excitation. 



The upper end of this experimental tract showed the usual resting electrical 

 difference between surface and cross section, which was compensated. 



The cut lumbar surface of each different column was now excited for 3 J seconds by 

 the interrupted current, 100 per second (Helmholtz side-wire), and the galvanometric 

 effect observed. 



Although the secondary coil stood at only 500, the preparation was very excitable. 

 Excitation of the anterior columns was followed by a slight but distinct effect, 22 with 

 left side, 28 with the right ; these, however, did not occur on repetition, and are 

 exceptional. 



On exciting the left lateral column, a deflection of 120 was observed, whilst on 

 exciting the left posterior column, a deflection of 215 was produced ; finally excitation 

 of the right lateral was followed by 100, of the right posterior, by 190. 



The general relationship of magnitude of electrical change evoked in the cord of the 

 Cat by lumbar excitation of the cross sectional area of its different columns is thus 

 the same as that obtained by dorsal excitation. 



