g4 PROFESSOR ALISON ON THE NERVES OF THE EYEBALL. 



change, e. g. in the number and rapidity of the beats of the heart, or of the peri- 

 staltic movements of the intestines ; in short, as HALLER long ago expressed it, a 

 change of the property of irritability itself, as resident in these muscular organs. 



Now, when we apply these observations generally, to the living actions of 

 those muscles which have their nerves from the sympathetic, I think we can be 

 at no loss as to the use of great part, at least, of the structure of this part of the 

 nervous system. These nerves place the organs which they supply in connexion 

 with the whole extent of the cerebro-spinal axis ; we know, from the observations 

 now stated as to the iris, that an influence may be transmitted to these organs 

 through any of the nerves entering any one of the ganglia ; we know, from such 

 experiments as those of LE GALLOIS and Dr WILSON PHILIP, as well as from the 

 effects of injuries on the human body, that injuries acting on any large portions 

 of the brain or spinal cord, affect the heart at least,. if not other of these organs, 

 nearly alike ; we know that, in the natural state, all these organs are peculiarly 

 under the control of what I have called sensorial influence, i. e. an influence re- 

 sulting from those changes in the nervous system which attend intense sensations 

 and emotions of mind; we know, from various facts, some of which I have elsewhere 

 collected,* that this sensorial influence, although often originating from an impres- 

 sion made on a single point, extends itself rapidly in different directions through 

 the nervous matter, and that it can cross from the sensitive portions of the nervous 

 matter to the motor portions, probably at any part of the spinal cord. The effect of 

 any arrangement which brings a particular muscle into communication with many 

 points of the cord, must be still more decided in regard to this sensorial influence, 

 than as to the influence of volition as affected by a plexus. The purpose of the 

 multiplied origins of the spinal accessory nerve, which appears, from the experi- 

 ments of VALENTIN and others, to transmit an influence to a greater number of 

 nerves, connected with the cervical plexus, than had been formerly suspected, 

 and therefore to be essentially concerned in many complex actions consequent on 

 sensation and emotion, is thus easily understood. Some observations already 

 published by Dr REID, shew more precisely that in the case of the heart, just as 

 in the case of the iris, the sensorial influence, or one exactly similar to it, affecting 

 the contractile power of the muscle, may be transmitted through different nerves 

 entering the ganglia, and so passing to the muscles ; for he found that a violent 

 blow on the head influenced the actions of the heart much less, when the sym- 

 pathetic and par vagum were cut in the neck, than when these nerves were en- 

 tire, shewing that a part of that influence passes through these nerves ; and on 

 the other hand, he found that when an animal in which these nerves had been 

 cut was under the impression of fear, its heart's actions were quickened nearly in 

 the usual way ; shewing that another part of that influence must pass through 



* Outlines of Physiology, p. 398. 



