v SPINAL COED AND NEEVES 303 



the morphological work of Bolk on both motor and sensory roots 

 in man. 



If we summarise the complicated results of these three authors 

 under a few heads, and for the moment pass over certain divergences 

 which will be discussed below, it may be said that : 



(a) "There is a true segmentation of the body-surface (Sherring- 

 ton's segrnental skin-field) as well as a true segmentation of the 

 muscles, which both correspond with the metamerism of the spinal 

 roots. There are certain exceptions to the strict parallelism 

 between the segmental innervation of the skin and of the 

 muscles assumed by Schroder van der Kolk, particularly in the 

 extremities, where during phylogenetic and ontogenetic evolution 

 the muscle segments often become more or less displaced in 

 relation to the segmental skin-fields. 



(&) While the skin segments (Bolk's dermatomes) form con- 

 tinuous fields, the muscle segments (Bolk's myotomes) are com- 

 pounded of portions of several muscles. Their metanieric 

 arrangement is less striking than in the dermatomes, but can 

 easily be demonstrated. 



(c) The metameric arrangement of the dermatomes and 

 myotomes in the neck and trunk is ring-shaped ; at the ex- 

 tremities it seems to be more complicated, but is intelligible from 

 the embryological development of these organs. 



(d) Each dermatome is partially covered by the adjacent, which 

 immediately precedes and follows it in the serial arrangement 

 (cranio-caudal direction). This fact, already known to Eckhard 

 and Tiirck, has been termed by Sherrington overlapping. Whether 

 a similar overlapping occurs among the myotomes is at present 

 unknown. 



(e) The sensory innervation of the muscles follows their 

 metamerism, not that of the skin. The metamerism of the pilo- 

 motor nerves is almost parallel with that of the skin. The 

 vasomotor innervation of the skin also corresponds approximately 

 with the dermatomes. 



These facts from the work of Sherrington, Eisien Eussell and 

 Bolk give an almost complete schema of the metamerism of the 

 skin and muscles (Fig. 180). There are, of course, divergences 

 that seem a priori inevitable in view of the difference of species 

 (man and monkey) and of method (physiological and morpho- 

 logical) under which the data were collected. 



Kocher's attempt (1896) to determine the segmental skin- 

 fields for man solely by deductions from clinical data was a 

 failure. A series of publications by the Dutch neurologist 

 Winkler and his pupils, Beyermann, Coenen, Langelaan, Van 

 Eynberk, show that the clinical data accord well with the diagrams 

 of Sherrington and of Bolk. 



Wichmann has recently collected from modern clinical 



