A text-book of physiology, for medical students and physicians . in proportion to the skill obtained, becomemore or less entirely reflex,—that is, involuntary. In learningsuch movements one must, as the saying goes, establish his reflexes,and the result can hardly be understood otherwise than by suppos-ing thai the continual adjustment of certain sensory impulses to certain co-ordinaled movements results in the formation of a moreor less complex reflex arc, a eel of pal hs of least resistance. Reflexes through Peripheral Ganglia Axon Reflexes.—Many attempts have been made by physiologists to a
A text-book of physiology, for medical students and physicians . in proportion to the skill obtained, becomemore or less entirely reflex,—that is, involuntary. In learningsuch movements one must, as the saying goes, establish his reflexes,and the result can hardly be understood otherwise than by suppos-ing thai the continual adjustment of certain sensory impulses to certain co-ordinaled movements results in the formation of a moreor less complex reflex arc, a eel of pal hs of least resistance. Reflexes through Peripheral Ganglia Axon Reflexes.—Many attempts have been made by physiologists to ascertainwhether or not reflexes can occur through the peripheral nerveganglia, lying outside the central nervous system. With regardto the posterior root ganglia, it has usually been supposed thatthey cannot exhiliit reflexes. When the posterior rool con-necting auch a ganglion to the cord is severed, then, accordingto our usual conception, the cells in the ganglia are cut offfrom all connections with the peripheral tissues by efferent REFLEX ACTIONS. 153. paths. This usual view may not, however, be correct. Onthe physiological side we have the fact (see p. 83) that stimu-lation of certain of the posterior root ganglia undei such cir-cumstances does give peripheral effectson the blood-vessels, causing a vasculardilatation in a certain region. On thehistological side Cajal* and others haveshown that some of these cells are providedwith a pericellular nerve network, whichis an afferent path so far as the cell is con-cerned, while the axon of the cell con-stitutes an efferent path. Whether thesecells form a special group of efferent cellslying within the sensory ganglion, orwhether they are sensory cells discharginginto the cord and stimulated reflexlythrough the nerve network as well asthrough the peripheral process of the axon,cannot be said. The subject is one fullof interest to physiology. In the gangliaof the sympathetic nerve and its appen-dages and in the similar gangli
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