100 



NERVOUS SYSTEM. 



regards the cerebral nerves, and especially the optic, auditory, and 

 olfactory, as afferent excitor nerves, along which impressions pass to 

 the central axis ; thence to be communicated to the motor nerves, and 

 thus give rise to combined muscular acts, or to irregular spasmodic 

 movements. Hydrophobia is adduced by him as a good illustration of 

 these cerebral reflex movements. The acknowledged excito-motory 

 phenomena in the disease may be induced. First. Through the nerves 

 of touch, as by the contact of water with the surface of the head, 

 hands, chest, lips, and pharynx. Secondly. By a current of air im- 

 pinging on the face or chest. Thirdly. By a bright surface, as a mir- 

 ror. Fourthly. By the sight of water ; and Fifthly. By the idea of 

 water, as when it is suggested to the patient to drink. 



The author has been in the habit of offering as an example of the 

 same kind, vomiting induced by the sight of a disgusting object. 

 Here the impression is first made upon the brain through an organ of 

 sense, and the reflex motor phenomena concerned in vomiting are in- 

 stantaneously excited; facts, which at least prove, that although the 

 gray matter of the spinal marrow may continue to execute its func- 

 tions, when those of the cerebro-spinal nervous system are suspended, 

 as during sleep or an attack of epilepsy, it is capable of being 

 excited to action by impressions made through the latter, in the same 

 manner as by impressions made on the afferent spinal nerves themselves. 



From all that has been said, it will be un- 

 Fig. 24. derstood, that each nerve as it issues from 



the spinal canal must be composed of various 

 fasciculi : one, sensory or of sensation, con- 

 nected with the posterior medullary tract, 

 and continuous with the medullary matter of 

 the brain ; another, connected with the ante- 

 rior medullary tract, and conveying the in- 

 fluence of volition from the brain along the 

 spinal cord and nerves to the muscles ; a 

 third, consisting of excitor fibres, terminating 

 in the gray or ganglionic matter of the cord, 

 and conveying impressions to it; and a 

 fourth, consisting of motor fibres, arising 

 from the gray matter of the cord, and con- 

 veying the nervous influence reflected to the 

 muscles. 



It would appear that a part of each root 



structure of the Spinal Cord, ac- enters the gray matter of the cord ; whilst a 

 cording to Stilling. p ar t is continuous with the white or medullary 



A. Posterior fibres continuous matter; and Dr. Stilling 1 affirms as the re- 



with the anterior of the same side, , _ 7 , , , f , ,,, ,. 



through the nucleus of the cord, suit oi his researches that ot the tibres oi 



B. Posterior fibres continuous with ,1 -nnctArinr rnnf<a QHTTIP fnrm lnnn<5 in tllP 

 the anterior of the opposite side. M* pOSlCr 



gray matter, and become continuous with 

 thbsp of the adterio? -I'oot's of the mme side; whilst others cross the 



,* Untersuchunge i uber die Textur des Ruckenmarks, von Dr. B. Stilling und Dr. J. Wal- 

 \zk,s.5l. Leipz, 1S42. 



