55fi Dr. C. S. Sherrington. On the Knee-jerk and the [Feb. 9, 

 DESCRIPTION OF PLATE 14. 



Diagram to show the connexions of 



(a.) The spinal nerves with the ganglia of the sympathetic chain. 



(b.) The grey rami of the ganglia with the skin. 



The diagram also shows the distribution of the sensory fibres of the spinal nerves 

 with the skin of the mid-dorsal line ; leaving out of account any overlapping of the 

 areas that may occur. 



The meaning of the several parts of the diagram is, for the most part, explained 

 by the lettering. 



In addition it must be noted that 



1. The broken lines indicate that the connexion shown by the line has been deter- 



mined by experiments on some other than pilo-motor fibres, e.g., by pupillo- 

 dilator or by sweat- nerve fibres. 



2. The connexion of the several spinal nerves with the sympathetic ganglia is not 



in all cases as it is represented in the diagram. There are individual varia- 

 tions. 



3. Any one spinal nerve is connected with certain of its ganglia by a consider- 



able number of fibres, and with others by very few. It is connected by few 

 fibres with either the uppermost or the lowermost, or with both uppermost 

 and lowermost, of its series of ganglia. Thus the 7th thoracic nerve sends 

 comparatively few fibres to the superior cervical ganglion, and the 3rd lumbar 

 nerve sends comparatively few fibres to the 5th lumbar sympathetic 

 ganglion. 



4. The distribution of the several grey rami to the skin also varies ; the extent 



of this variation has been described in the text. In the scheme given here, 

 the case is taken when the 7th and 8th thoracic and the 6th lumbar nerves 

 do not run to the mid-line of the back. 



5. The dotted line stretching from the upper end of the skin area of the grey 



ramus of the 1st coccygeal ganglion indicates that the area of the 3rd sacral 

 grey ramus is usually supplied by fibres from the coccygeal ganglion. It 

 will be noticed that only the base and tip of the tail are represented. 



II. " Note on the Knee-jerk and the Correlation of Action of 

 Antagonistic Muscles." By C. S. SHERRINGTON, M.A., M.D. 

 Communicated by Professor M. FOSTER, Sec. R.S. Re- 

 ceived February I, 1893. 



(From the Physiological Laboratory, St. Thomas's Hospital.) 



The muscular reaction known as the knee-jerk is notoriously 

 affected by conditions obtaining in what is often described as a reflex 

 arc, consisting of afferent and efferent paths, and a centre situate in 

 the lumbar portion of the spinal cord. I recently* described experi- 

 ments determining more particularly than hitherto the locality of the 

 muscular and nervous mechanism on which the jerk depends. I 

 showed that the muscular portion of this mechanism consists mainly 

 * ' Journal of Physiology,' vol. 13, p. 666. 



