ROLLING AND TURNING MOVEMENTS. 709 



'' 10. Portion of the medulla from winch the facial nerve arises (Brown-Sequard) ; 



" 11. Optic nerves ; 



" 12. Semicircular canals (Flourens) ; auditory nerve (Brown-Sequard)." 



To the parts above enumerated, Vulpian adds the upper part of the cervical portion 

 of the spinal cord. 



The movements which follow unilateral injury of the parts mentioned above are of 

 two kinds; viz., rolling of the entire body on its longitudinal axis, and turning, always in 

 one direction, in a small circle, called by the French the movement of manege. A capital 

 point to determine in these phenomena is, whether these movements be due to paralysis 

 or enfeebleraent of certain muscles upon one side of the body, to a direct or reflex irrita- 

 tion of the parts of the nervous system involved, or to both of these causes combined. The 

 experiments of Brown-Sequard and others conclusively show that the movements may be 

 due to irritation alone, for they occur when parts of the encephalon and the upper por- 

 tions of the cord are simply pricked, without section of fibres. When there is extensive 

 division of fibres, it is probable that the effects of the enfeeblement of certain muscles are 

 added to the phenomena produced by simple irritation. The most satisfactory explana- 

 tion of these movements is the one proposed by Brown-Sequard, who attributes them to 

 a more or less convulsive action of muscles on one side of the body, produced by irrita- 

 tion of the nerve-centres. He regards the rolling as simply an exaggeration of the turn- 

 ing movements, and places both in the same category. 



We do not propose to enter into an elaborate discussion of the above experiments, for 

 the reason that they do not seem to have advanced our positive knowledge of the func- 

 tions of the nerve-centres. In some of them, the movements have been observed toward 

 the side operated upon, and in others, toward the sound side. These differences probably 

 depend upon the fact that, in certain experiments, the fibres are involved before their 

 decussation, and in others, after they have crossed in the median line. In some instances, 

 the movements may be due to a reflex action, from stimulation of afferent fibres, and in 

 others, the action of the irritation may be direct. Judging from the fact that most of the 

 encephalic commissural fibres are apparently insensible and inexcitable under direct 

 stimulation, it is probable that the action is generally reflex. 



In concluding the physiological history of the encephalon, we have only to refer to 

 the general properties of certain of the peduncles. Longet found that direct irritation of 

 the superior and the inferior peduncles of the cerebellum, in rabbits, produced pain, but 

 the disturbance consequent upon exposure of the parts did not allow of any accurate 

 observations upon the movements. He says nothing of the general properties of the mid- 

 dle peduncles or of the peduncles of the cerebrum. 



CHAPTER XXII. 



SYMPATHETIC NERVOUS SYSTEM-SLEEP. 



General arrangement of the sympathetic system Peculiarities in the intimate structure of the sympathetic ganglia 

 and nerves General properties of the sympathetic ganglia and nerves Functions of the pympatht -tic M^nn 

 Vaso-motor nerves Reflex phenomena operating through the sympathetic system Trophic centres and nerves 

 (so called) Sleep General considerations Condition of the organism during sleep Dreams R. -tlex mental phe- 

 nomena during sleep Condition of the brain and nervous system during sleep Theories of sleep Anaesthesia 

 and sleep produced by pressure upon the carotid arteries Differences between natural sleep and stupor or 

 coma Regeneration of the brain-substance during sleep Theory that sleep is due to a want of oxygen Condi- 

 tion of the various functions of the organism during sleep. 



WHILE there are certain points in the physiology of the sympathetic nervous system 

 that are perfectly well established, it must be admitted that its functions are, in many 

 respects, obscure, and that our positive knowledge of its general properties and its rela- 



