PROFESSOR ALISON ON THE NERVES OF THE EYEBALL. 69 



more or less directly on Sensation ; that if we are certain of any movement in 

 an organized body being altogether independent of sensation, and affording no 

 indication of any mental act, we should refer it to the same class as movements 

 in vegetables ; and that in designating such movement as Organic, but not Animal, 

 we express a distinction of essential importance in physiology. 



It has indeed been lately maintained by several eminent physiologists, who 

 have studied the indications' of what is now called the Reflex Function of the 

 Spinal Cord, that many living actions, such as respiration, deglutition, coughing, 

 sneezing, and vomiting, the evacuation of the bowels and bladder, and even the 

 movements by which irritations of the surface are avoided or repelled, certainly 

 attended in the natural state by sensations, and usually thought to indicate sen- 

 sation, and therefore to belong to the department of animal life, are independent 

 of sensation, and ought, therefore, according to the principle above stated, to be 

 referred to that of organic life. But although it is well ascertained that move- 

 ments may be excited in perfectly paralytic limbs, by irritations applied to the sur- 

 face, which must be carried back to the sensitive, and cross from thence to the 

 motor portions of the spinal cord connected with those limbs ; and therefore that 

 the whole series of nervous actions which takes place when any of these reflex or 

 sympathetic actions are excited, may be in some degree imitated by mechanical 

 irritation of the nervous matter, independently of sensation ; yet when it is in- 

 ferred from this fact that, in the entire and healthy body, Sensation does not inter- 

 vene, as a part of the sequence of cause and effect on which such actions depend, 

 this theory overlooks so much of what has been formerly ascertained and pointed 

 out in regard to them, that I do not think we can expect it long to hold its ground 

 in physiology. 



The movements which are excited by irritation of the sensitive nerves, in 

 the undoubted absence of sensation (which of course can only be known in the 

 human body in the state of disease), are general and irregular, and have not the 

 character of selection and adaptation to particular purposes, which is essential to 

 the useful application of any such actions in the living body. And when it is sup- 

 posed that such movements as respiration, coughing, or deglutition, are equally 

 independent of sensation, we not only overlook this, their essential character, of 

 selection of individual nerves and adaptation to particular ends, but disregard the 

 following facts, long ago stated in evidence, that sensations intervene in the pro- 

 cess by which they are excited. 



1. In various cases, impressions on the sensitive nerves of different parts 

 of the body excite the same sensation, and then the same reflex or sympathetic 

 action follows, as when intense nausea results from changes whether in the 

 brain, fauces, stomach, bowels, liver, or kidneys, and is in each case followed by 

 the same act of retching, or when a full inspiration follows the dashing of cold 

 water on the face, breast, abdomen, or extremities. 



