SPINAL COED AND NERVES 



307 



gradually to the surrounding and the more peripheral parts of the 

 dermatome. These areas correspond with the points at which the 

 cutaneous nerves enter the skin. 



In another series of experiments Winkler and Van Rynberk 

 attempted to decide the question whether the four or five rootlets, 

 which make up each dorsal root, have a localised or a diffused 



v ct 



Fio. 182. Diagram of dermatomes of the trunk of the body. (Winkler and Van Rynberk.) All 

 six diagrams show a central area shaded dark and a marginal area shaded light ; d, median dorsal 

 line; I, lateral line ; r, ventral median line ; ?|e, centre of maximal dorsal innervation ; +, centre 

 of maximal lateral innervation. A shows the complete form of the central area, which is isolated 

 only in the most successful operations ; in B, C, D, E there is an increasing reduction of the 

 sensory central area owing to greater traumatic lesions or to partial section of the roots ; at F 



the .whole dermatome is insensitive save the first area marked ***** which corresponds to 

 the point of maximal dorsal innervation known as the ultimum moriens of the dermatome. 



distribution in the dermatome. Their results showed that partial 

 transection of the root has the same effect as a complete section, 

 except that the central area of complete insensibility is reduced 

 as indicated in Fig. 182. The diagrams B, C, D, E show the 

 various degrees of restriction of sensory area shown in such cases. 

 During the period of shock after the operation a few points only 

 may be found near the median dorsal line (diagram F), in which 

 sensibility persists in the midst of an analgesic area. This point, 



