98 NERVOUS SYSTEM. 



tnotory system belong all spasmodic and certain paralytic diseases. 

 He adds, that these two parts of the nervous system influence each 

 other both in health and disease, as they both influence the ganglionic 

 system. 1 



The views of Dr. Hall on the excito-motory function have been em- 

 braced by Muller, 2 Grainger, 3 Carpenter, 4 and indeed, with more or less 

 modification, by almost all physiologists. 5 Dr. Carpenter inferred from 

 his inquiries, that the actions most universally performed by a nervous 

 system are those connected with the introduction of food into the di- 

 gestive cavity, and that we have reason to regard this class of actions 

 as every where independent of volition, and perhaps also of sensation, 

 the propulsion of food along the oesophagus, in man, being of this 

 character ; that for the performance of any action of this nature, a 

 nervous circle is requisite, consisting of an afferent nerve, on the peri- 

 pheral extremities of which an impression is made, a ganglionic cen- 

 tre, where the white fibres of which that nerve consists terminate in 

 gray matter, and those of the efferent nerve originate in like manner ; 

 and an efferent trunk conducting to the contractile structure the motor 

 impulse, which originates in some change between the gray and white 

 matter ; that in the lowest animals such actions constitute nearly the 

 entire function of the nervous system, the amount of those involving 

 sensation and volition being very small ; but as we ascend the scale, 

 the evidence of the participation of true sensation in the actions neces- 

 sary for acquiring food, as shown by the developement of special sen- 

 sory organs, is much greater; but that the movements immediately 

 concerned with the introduction of food into the stomach remain under 

 the control of a separate system of nerves and ganglia, to the action 

 of which the influence of the cephalic ganglia the special if not the 

 only seat of sensibility and volition is not essential; that, in like 

 manner, the active movements of respiration are controlled by a sepa- 

 rate system of nerves and ganglia, and are not dependent upon that of 

 sensation and volition, although capable of being influenced by it ; 

 that whilst the actions of these systems are, in the lower tribes, almost 

 entirely of a simply reflex character, we find them, as we ascend, gra- 

 dually becoming subordinate to the will ; and that this is effected by 

 the mixture of fibres proceeding directly from the cephalic ganglia with 

 those arising from their own centres ; that the locomotive organs, in 

 like manner, have their own centres of reflex action, which are inde- 

 pendent of the influence of volition, perhaps also of sensation ; that 

 the influence of the will is conveyed to them by separate nervous fibres, 

 proceeding from the cephalic ganglia, and that similar fibres probably 

 convey to the cephalic ganglia the impressions destined to produce sen- 



1 Principles of the Theory and Practice of Medicine, by Marshall Hall, M. D., F.R.S., p. 

 243, London, 1837, and American edit, by Drs. Bigelow and Holmes, Bost., 1839. 



2 Handbuch der Physiologic, s. 333, and s. 688, Coblenz, 1835, 1S37, or the English trans- 

 lation by Dr. Baly, i. 707, London, 1838. 



3 On the Structure and Functions of the Spinal Cord, London, 1837. 



4 Op. cit. 



5 Todd and Bowman, the Physiological Anatomy and Physiology of Man, p. 312. London, 

 1845. 



