274 MESSRS. F. GOTCH AND V. HORSLEY 



(1.) Latent Period. The interval of time occupied in the passage of a nerve impulse 

 from the afferent to the efferent side of a (reflex) bul bo-spinal centre is given on 

 p. 481, to which reference is directed. (WuNDT, EXNER, and others.) 



(2.) Excitability. This function of the grey bulbo-spinal matter is modified by the 

 same causes as those which influence the Cortex, see pp. 272 and 483. 



When the excitability of the cord is raised, e.g., that of the distal segments after 

 section, these latter may discharge in a coordinated fashion, see p, 423, as was first 

 observed by SCHIFF. 



(3.) Mode of Discharge. The bulbo-spinal centi*es, like the cortex, present three 

 modes of discharge, but not in the same degree, e.g., the combined sequence of tonus 

 and clonus though sometimes present, see pp. 483-499, nevertheless occurs but rarely. 

 Further, as evidenced by muscular responses, the bulbo-spinal centres appear to dis- 

 charge at regular intervals under certain conditions of isolation and excitation, e.g., 

 ankle clonus (V.H.). For further detail see p. 483. 



(4.) Nature of the Discharge, (a.) As in the case of the cortex cerebri the charac- 

 ter of the muscular response to excitation of the cord is different from that seen when 

 the excitation is directly applied to the nerve. 



(b.) The tonic contraction is usually developed more rapidly than that obtained 

 from the corona radiata.- 



(c.) The rhythm of the intermittent muscular contractions, fused or not, is from 

 8 to 10 per second or frequently the early multiples of this rate. 



(5.) Relation of the Discharge to the Parts of the Body. (a.) Localisation of the 

 representation of the gross divisions of the body to different regions of the bulbo- 

 spinal apparatus is well marked. (All authors.) 



(b.) Localisation of the representation of the segments of the gross divisions and the 

 character of their respective movements to different root-origins in the grey matter. 

 (FERRIER and YEO, SCHIFF, FORGUE, BEEVOR.) 



II. PATHS. 



Functional Activity of the Efferent Paths. 



The graphic method only permits of a limited analysis of paths, i.e., fibres, inasmuch 

 as there is of necessity included the bulbo-spinal system of centres for the purpose of 

 giving the muscular contractions used for record. Hence no result by the graphic 

 method can be regarded as pure ; moreover, it only furnishes information upon the 

 functions of efferent paths. 



In fact, there is no direct evidence forthcoming from any method of observation, 

 except that of the galvanometer, to prove that the paths themselves in the cord 

 are excitable. Indeed, it has long been held by many physiologists that all effects 

 obtained from stimulation of the spinal cord are due to primary and progressive 



