ON THE MAMMALIAN NERVOUS SYSTEM. 273 



(3.) Mode of Discharge. The impulses generated in the cortex, and which pass 

 down to the muscles may, according to the duration and intensity of the stimulus, be 

 of the nature of (a) single discharges producing one muscular contraction ; or (6) com- 

 pound discharges producing tonic muscular contraction, or (c) a combination of tonic 

 and clouic contractions. (FRITSCH, HITZIG, FERRIER, MUNK, FRANCK, and all other 

 authors.) This last combination is to be looked upon as the complete discharge of the 

 cortex, vide infra and pp. 345. 349, &c. 



(4.) Nature of the Discharge. (a.) The single muscular contraction is more pro- 

 longed, and ceases more gradually than that elicited by a single stimulus applied to 

 the motor nerve. (FRANCK, confirmed by ourselves.) 



(6.) The tonic contraction is regarded by most authors as a fusion of contractions 

 evoked by many discharges. (FRANCK, SCHAFER and HORSLEY ; vide infra " Corona 

 Radiata.") 



(c.) The tonic and clonic contractions occur in the order mentioned, and are to be 

 regarded as the muscular response to a complete cortical discharge, i.e., comprising a 

 primary effect and after-effect. 



(d.) The rate or rhythm with which these muscular responses* appear to succeed 

 one another has been variously estimated by different observers in different animals 

 and with different instruments, and has been ascertained to be from 8 to 10 per 

 second. 



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

 representation of the gross divisions of the body to definite areas of cortex. (FRITSCH 

 and HITZIG, FERRIER, MUNK, LUCIANI, SCHAFER, BEEVOR, HORSLEY.) 



(6.) Localisation of the representation of segments of the gross divisions to definite 

 areas of cortex. (BEEVOR and HORSLEY.) 



(c.) Localisation of the representation of the character of the various movements of 

 segments to definite areas of cortex. (BEEVOR and HORSLEY.) 



B. Spinal Cord. 



Under this heading we will group the phenomena associated with the functional 

 activity of the system of bulbo-spinal centres, i.e., those in which the efferent paths 

 terminate. It may not be superfluous to add that the information furnished by the 

 graphic method does not differentiate the complex structure of a bulbo-spinal centre, 

 and that it can only yield a record of the combined action of mainly afferent and 

 mainly efferent corpuscles in the posterior and anterior divisions of the grey matter. 

 All methods of observation hitherto employed involve the activity of the whole 

 apparatus, and this must be borne in mind in considering the following facts. 



* The tracing waves indicating the contractions are frequently summated. (HORSLEY.) 

 Quite recently the value of these waves as indications of rhythmical nerve discharges has been con- 

 tested. (WEDKXSKII, HAYCBAFT.) 



MDCCCXCI. B. 2 N 



