680 FOURTH REPORT 1834. 



6. Experiments upon the Sympathetic Nerve. — No ejiperi- 

 ments upon this nerve have hitherto exhibited any signs of sen- 

 sation or muscular motion of any kind whatever. Its division 

 is never followed by any visible effect. 



Remarks. — By these observations some researches of other ex- 

 perimenters stand confirmed, whilst others are contradicted; the 

 necessary consequence of discrepancies, often arising from the 

 different modes of applying certain terms. Although the my- 

 sterious properties and actions of the nerves may never be com- 

 pletely unravelled, yet much has been effected by the successive 

 and combined efforts of physiologists of different ages and 

 countries. 



The presentinvestigationleads to the assumption, that one only 

 of those nerves which derive their roots from the brain itself 

 is, according to the definition laid down, a nerve of sensa- 

 tion. This is the larger and ganglionic division of the fifth 

 nerve, whereby animals are enabled to examine by touch and to 

 feel. 



With regard to the other nerves subjected to experiment in 

 this inquiry, none of them appear to possess in themselves any 

 power to excite consciousness or feeling directly. Some of theni 

 are simply nerves of motion, and they transmit no other impres- 

 sions but such as excite local muscular motion, limited to the 

 muscles which they supply. Others, again, seem to possess a 

 property of a different description from either of the two former 

 kinds. One of these, the eighth for example, appears to be so 

 intimately connected with the respiratory function as to be capa- 

 ble of influencing it in a most remarkable degree, without ex- 

 hibiting any sign of sensation in itself, or of simple and direct 

 muscular contraction. 



It is a most remarkable fact, that when a nerve which influ- 

 ences respiration is divided, and the upper division is bruised or 

 compressed for a few seconds, the same effects occur as when 

 the irritation is applied to the entire nerve. This phaenomenon 

 affords matter of curious and interesting speculation with regard 

 to the relations which subsist between the nervous and the re- 

 spiratory functions. 



The further pursuit of this inquiry may lead to some further 

 development of facts hitherto exposed in some instances to doubt 

 and controversial discussion. 



Dr. Hall was necessarily absent at one of the experiments, 

 that on the ninth nerve ; but he feels perfectly satisfied with 

 the joint testimony of Mr. Field and Mr, Broughton. 



