NERVOUS SYSTEM. 99 



sations; that the stomato-gastric, respiratory, and locomotive centres 

 are all united in the spinal cord of the vertebrata, where they form one 

 continuous ganglionic mass, and that the nerves connected with all these 

 likewise receive fibres derived immediately from the cephalic ganglia; 

 and lastly, that whenever peculiar consentaneousness of action is re- 

 quired between different organs, their ganglionic centres are united 

 more or less closely ; and that the trunks themselves are generally con- 

 nected by bands of communication. 



On the whole, in the present state of our knowledge, we are justified, 

 perhaps, in adopting the systematic summary of the functions of the 

 nervous system, and the general purposes to which it is inservient, as 

 given by the writer last cited. 1 1. The nervous system receives im- 

 pressions, which, being conveyed by its afferent fibres to the sensorium, 

 are there communicated to the conscious mind; and are inservient, in 

 some manner, to the acts of that mind. As the result of these acts, 

 a motor impulse is transmitted along efferent nerves to particular mus- 

 cles, which excites them to contraction. Of these acts the encephalon, 

 and nerves communicating with it, are the organs. 2. Certain parts 

 of the nervous system receive impressions, which are propagated along 

 afferent fibres that terminate in ganglionic centres distinct from the 

 sensorium. In these, a reflex motor impulse is thus excited, which is 

 transmitted along efferent trunks proceeding from those centres, and 

 excites muscular contraction without any necessary intervention of sen- 

 sation or volition. The organs of this function are the gray matter of 

 the spinal cord, which is not continuous with the fibrous structure of 

 the brain, and the trunks connected with it. It is the true spinal or 

 excito-motory system of Dr. Hall. 3. There is yet a division of the 

 nervous system, which appears to have for its object to combine and 

 harmonize the muscular movements immediately connected with the 

 maintenance of organic life. It may likewise influence, and connect 

 with each other the functions of nutrition, secretion, &c. ; although 

 these like the muscular movements immediately connected with the 

 maintenance of organic life are doubtless essentially independent of 

 it ; and as has been shown can be carried on where it does not exist. 

 The organ of these acts is the great sympathetic. Of late as will be 

 seen hereafter Dr. Carpenter 2 has contended with much force for the 

 existence of a series of sensory ganglia, separate and distinct from those 

 that compose the cerebrum and cerebellum " ganglia of the nerves of 

 sensation, common and special, which are superposed, as it were, on 

 the medulla oblongata," and which, together, constitute the real sen- 

 sorium. 



It has been urged by Dr. Laycock, 3 in a paper read before the Bri- 

 tish Association at York, in accordance with views published by him 

 four years previously, that the brain, although the organ of conscious- 

 ness, is subject also to the laws of reflex action; and that in this re- 

 spect it does not differ from other ganglia of the nervous sjsteni. ( He 



1 Human Physiology, p. 79, London, 1842.. 



a Principles of Human Physiology, 4th Amer. edit., p. 320, Philad., 1850. 



3 British and Foreign Medical Re vievf, Jap ( ., 184 X p 298. 



