THE MAMMALIAN NERVOUS SYSTEM 65 



distribution of nerve-cells in both the dorsal and ventral gray 

 columns at each of these levels and compare in detail the group- 

 ing of the cell bodies in the ventral columns. Draw these 

 groups of cells in the four outline sketches of the spinal cord. 

 The ventro-medial group of neurones supplies the muscles of 

 the back, the dorso-lateral and ventro-lateral groups chiefly the 

 muscles of the limbs, and the intermedio-lateral groups the 

 motor sympathetic fibers (see Barker ('01), pp. 883-914; Bruce 

 ('01) ; Cunningham ('15), Fig. 467, p. 525; and Fig. 468, p. 529, 

 also summary on p. 527; Curtis and Helmholz ('11); Herrick 

 ('18), Fig. 59; Piersol ('16), Figs 895-901, pp. 1041-1046; 

 Quain ('09), Fig. 112, p. 78; Rauber-Kopsch ('12), Figs. 35- 

 64, pp. 39^42. 



On the neurons of the dorsal gray columns and their connec- 

 tions consult Ramon y Cajal ('09), Vol. I, pp. 307-340. 



66. The spinal cord performs two important groups of 

 functions: (1) it contains the central mechanisms of the intrin- 

 sic spinal reflexes; (2) it serves as a path of conduction 

 between the sensory and motor spinal nerves and the higher 

 correlation centers of the brain. For a list of the tracts belong- 

 ing to the second group, see Section 101. Here attention 

 should be directed to the intrinsic reflex connections of the cord. 

 (On this subject see the very interesting cases reported by 

 Riddoch, 1917.) The cell bodies of the neurons involved in 

 these reflexes lie in the gray matter, and their axons form the 

 greater part of the fasciculus proprius, through which reflex 

 impulses are transmitted in both ascending and descending 

 directions between the different levels of the cord. With the 

 aid of your reference books build up a clear picture of the mode 

 of connection of these neurons in typical spinal reflexes. See 

 Herrick ('18), Figs. 60, 61; Herrick and Coghill ('15); Howell 

 ('18), Chapters VII, VIII; Morris ('14), Fig. 610, p. 767; 

 Quain ('09), p. 99; Sherrington ('06), Chapters I to IV, espe- 

 cially the diagram on p. 46; Starling ('15), Chap. VII; Starr, 

 Strong, and Learning ('96). 



67. Functional analysis of the cord. (a) The classification of 

 the functional systems adopted in this work should here be re- 

 viewed (see Sections 15 to 19, 47, 52 to 57, and the references 

 there given) . The somatic sensory systems include the nerves, 



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