86 PROFESSOR ALISON ON THE NERVES OF THE EYEBALL. 



with the question, in what manner the fifth nerve is qualified for transmitting 

 downwards the effect which sensations, even in distant parts of the body, and 

 emotions or passions of the mind, have on the circulation through the eye, and 

 on all its secretions. 



The instance of the lacrymal gland, and of the mamma, (which, according to 

 the dissections of MULLER, has its nerves merely from the intercostals, to the ex- 

 clusion of the sympathetic,) are enough to shew, that the most intense agency of 

 mental emotion may take place through the nerves of common sensation. 



I think Dr MARSHALL HALL has good reason for the opinion which he has 

 stated, that as the nerves which supply most of the internal organs of secretion, 

 and of organic life in general, are ganglionic, and as the circulation in the 

 eye itself is liable to influence from section of the sympathetic nerve as well 

 as of the 5th, it is probable that the Gasserian ganglion, and the ganglia on 

 the sensitive roots of the spinal nerves generally, must be designed for the in- 

 fluence of these nerves on secretion and nutrition, not for their functions in 

 regard to sensation ; but it seems to me much more doubtful, whether MULLER 

 is right in his conjecture, that the grey matter of the ganglia, and the grey fibres 

 passing from them along the nerves, are the parts of the nervous system designed 

 exclusively to affect the organic functions of secretion and nutrition. There are 

 no experiments to shew any such peculiar power in the grey matter of the ner- 

 vous system ; and I can state one fact which shews unequivocally that if it is, as 

 MULLER supposes, through the grey matter in the Gasserian ganglion, and of the 

 branches of the sympathetic which communicate, beyond that ganglion, Avith the 

 fifth nerve, that any emotions or sensations affect the secretions of the eye, that 

 grey matter must itself be acted on by the substance of the fifth nerve behind 

 the ganglion. For in one of the cases of palsy, affecting the fifth nerve on 

 one side, which was long under observation in the clinical ward, it was quite 

 obvious that neither emotions of mind, nor sensations excited in the sound nostril, 

 or in other parts of the body, affected the eye of the palsied side, which, although 

 inflamed, remained always dry when the other was suffused on such occasions. 

 Now, in this case it was ultimately ascertained by dissection, that the diseased 

 (and ultimately wasted) portion of the nerve was behind the Gasserian ganglion, 

 between it and the origin on the crus cerebelli ; from which it appears quite cer- 

 tain, that the influence of mental sensation and emotion must pass downwards 

 through this portion of the nerve (which I believe hardly contains any grey fibres) 

 on its way from the sensorium commune to the eyeball. 



Whatever may be the use of the grey matter in the ganglia, or in other parts 

 of the nervous system, I think we cannot doubt that there is here a grand excep- 

 tion to the principle which has been laid doAvn by several authors, that the same 

 nerve is never employed to convey impressions upwards to the sensorium and 

 downwards to the extremities of the nerves. At least, if there be a set of nerves 



