Spinal Cord 23 



line of entry of the dorsal roots is marked by a superficial 

 groove, the dor so -lateral groove, and between this and the 

 dorsal median fissure is an intermedio-lateral groove, from 

 which also a connective tissue septum extends inward. The 

 last mentioned septum, which appears only in the upper levels 

 of the spinal cord, divides the dorsal funiculus into a lateral 

 fasciculus ctineattis {column of Burdach) and a medial fascicidus 

 gracilis {column of Goll) . 



The various functional pathways, or fibre-tracts, within 

 these funiculi cannot be distinguished in normal adult material, 

 and have to be traced by experimental methods or by a study 

 of development. The only exceptions to this statement in 

 the case of the rat are the cortico-spinal tract and the tract 

 of Lissauer, which are described below. Such analyses have 

 not been made in the spinal cord of the rat, but as the general 

 pattern appears to be essentially similar throughout the 

 mammalia, a brief account of the pathways, based chiefly on 

 the human subject, is included here. A diagram of the 

 arrangement in the rabbit is also given in Fig. 2. 



General Somatic Afferent System. 



The peripheral receptive elements of this system fall into 

 two groups, exteroceptors and proprioceptors, of which the 

 first are stimulated by touch, pressure, heat, or cold, pain 

 due to excessive stimulation also being included usually in 

 this group, while the second transmit impulses arising in the 

 muscles, joints, etc. Impulses of this character from any 

 part of the animal except the head are carried to the spinal 

 cord, where they are passed on to secondary fibres which are 

 grouped according to the particular one of the above types 

 of sensation which they subserve. 



Upon entering the spinal cord, each somatic sensory fibre 

 typically divides into two branches, which run up and down 

 the cord respectively, the ascending branch being the longer. 

 The fibres bearing pain and temperature impulses soon end 



