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the nucleus cuneatus seems to stand in similar relation to fibres from the roots 

 at the top of the cord. 



The cell-processes of the Gasserian ganglion, on entering the bulb in its 

 pontine portion, bifurcate into long descending and short ascending stems. 

 Some of the latter join the middle cerebellar peduncle ; most, however, end in 

 the front (upper) part of the grey matter in the bulb called the sensory nucleus of 

 the fifth. The former descend close outside this and give collaterals into it ; the 

 descending stems, grouped just lateral to the substantia Eolandi, course back- 

 wards, some of them even so far as the level of the second cervical segment. 

 The petrous and jugular trunk ganglia of the glosso-pharyngeal vagus nerves 

 are equivalent to spinal ganglia. The descending stems, resulting from the 

 dichotomy of their fibres, run back as a circumscript bundle, fasciculus 

 solitarius, into the hindmost fourth of the bulb. Both they and their shorter 

 ascending stems give off and end in collaterals to the grey nucleus of ending 

 of the glosso-pharyngeal vagus in the floor of the fourth ventricle. 



The transverse extent of the region of intraspinal ending of the spinal 

 aiferent root includes in the uncrossed half of the cord the whole of the 

 spongiosa, and some end in the substantia Rolandi of the dorsal horn. 1 

 The root-collaterals traceable far across the spongiosa into the region of the 

 efferent root cells in the homonymous ventral horn are often called the 

 "reflex collaterals"; they perhaps constitute the ending of the afferent path 

 for some of the simplest and most direct of spinal reflex movements. 

 Root-collaterals form almost entirely the dorsal commissure especially in man 

 (v. Lenhossek), and end in the crossed grey matter; but none contribute to 

 the ventral commissure. 



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The efferent root cells are intraspinal in position. They lie in the 

 grey matter, chiefly in its ventral region. Each possesses numerous 

 dendrons, and a single axon. 



The grouping of the efferent root cells is segmental, in the sense that they 

 lie in the cord at the same segmental level as the segmentally arranged nerve 

 roots to which they contribute. But in some regions there is very consider- 

 able overlapping of the contiguous segmental fields to which they are 

 peripherally distributed. In the limb and neck regions of the cord the root 

 cells in the ventral horn are very distinctly collected into subgroups. These 

 groups are probably assemblies of cells, that collectively innervate particular 

 groups of muscles. Probably all the largest of the efferent root cells conduct 

 to skeletal muscles. The axons of the vast majority of the motor root cells 

 pass to muscles of the homonymous side. 2 The medio-ventral group of the 

 ventral horn is perhaps distributed to the muscles lying along the vertebral 

 axis. It seems, however, to include mediate cells, the " commissure group " 

 of v. Lenhossek, besides root cells. In the brachial and lumbo-sacral enlarge- 

 ments there is added to the grey matter of the ventral horn a huge 

 lateral region, in which lie several subgroups of large efferent root cells. 

 Of these there is one which, from its position in the frontal plane of the 

 grey horn, is called the dorso-lateral subgroup. To it has been attributed 

 the innervation of hand (and foot) muscles, especially of palmar (and plantar). 

 The topography of this subgroup along the length of the cord agrees with the 

 latter view, and with its atrophy after amputation of the end of the limb. 

 After amputation even at shoulder or hip, or after the limb has been rendered 

 apaesthetic by severance of the sensory roots, it is the group which suffers most 

 severe regressive change. In the limb thus rendered apaesthetic one niove- 



1 v. Lenhossek, "Derfein. Baud. Nervensystenis," 2te Aufl., Berlin, 1895. 



2 A. S. F. Grunbaum, Journ. Physiol., Cambridge and London, 1894, vol. xvi. p. 365; 

 Paladino. Arch. Hal. de bio/., Turin, tome xxii. p. 1. 



