I have ascertained by several experiments that the inhalation of ether has considerable effect in conuolling the natural polar state of the cord, as well as that which may be produced by strychnine. A pigeon deprived of its cerebral hemispheres lives in a state of sleep for a considerable time ; it flies when thrown in the air, spreading and flapping its wings ; stands when placed on its feet. A bird thus mutilated was made to inhale ether ; it could not stand, and when thrown into the air it fell to the ground like a heavy log, its wings remaining applied to the sides of its body, or if the wings were drawn out as it vvas thrown into the air, they quickly collapsed. As soon as the effects of the ether had passed off, it stood and flew as before. I gave strychnine to a rabbit, a guinea-pig, and a dog, so as to excite the tetanoid state. Immediately the spasms showed themselves, I brought it un der the influence of ether ; the spa.sms ceased immediately, and the animal became perfectly relaxed ; but as soon as the effects of the ether passed off, the spasms came on again, hut were soon subdued by a fresh inhalation of ether. And thus I found that the life of au animal poisoned by strychnine could be greatly pro longed through successive inhalations of ether ; for animals of the same kind, poisoned by equal doses of strychnine, but not subjected to the influence of ether, perished very rapidly.
The examples which show that the spinal cord possesses the power of reflecting sensitive impressions are chiefly derived from disease. Every practitioner is familiar with the pain in the knee which accompanies the early stages of disease of the hip joint. The patient some times refers his sufferings so exclusively to the former joint, that the disease of the latter may be entirely overlooked by his medical atten dant. Yet the really painful part is healthy, while the hip joint is the seat of a morbid process. The pains which are felt in the thighs from the presence of a stone in the bladder, and the itching which is referred to the extre mity of the prepuce from the same cause, are phenomena of the same nature. Pain in the right shoulder from irritation of the liver is a well-known sympathetic sensation : sometimes this pain extends over a very large surface.
Numerous other instances of similar sympa thetic phenomena might be adduced, but the above are sufficient for our present purpose. Taking into account the well-proved fact that nerves form no real junction of their fibres in their anastomoses, and that there is no more than a simple juxta-position of the nerve-tubes in these anastomoses, it is plain that we must trace these fibres up to the nervous centres to discover any connection between the fibre first irritated and that to which pain is referred. In the case of hip-joint disease, the nerves of the muscular coat of the bladder are the usual means by which the action of this viscus is promoted. It is possible that, as with the rec tum, under peculiar circumstances the physical stimulus acting reflexly on the muscular fibres themselves may come in aid of that of volition ; but such a mode of action is not the ordinary one. A line of argument similar to that which disproves the reflex nature of the action of the sphincter ani tells equally against that of the sphincter vcsicm. Were the action of this mus cle reflex, it ought to remain perfect when ever a sufficiently large segment of the cord remains in connexion with the bladder. Now
when the spinal cord is severed in any region so as to occasion paralysis of the lower extre mities, there is almost always incontinence of urine from the removal of voluntary influence from the sphincter vesicm : such ought not to be the case, if Dr. Ilall's views were correct.
Respecting the cardia and the valvula coli, I shall only remark that the evidence of reflex action is extremely defective. The cardia, in deed, has no sphincter ; it is closed by the lower circular fibres of the cesophagus, which keep that canal in a contracted state by their tone or passive contraction. The pylorus is provided with a sphincter muscle of great power, which closcs that orifice by its passive contraction, and which in animals recently killed will continue to close the orifice as long as the muscle retains its tone. If an animal be killed during stomach digestion, the stomach noay be removed, and yet the pylorus will retain the food in it even against gravity ; the cardia, if 3. sufficient portion of the cesophagus be retained, will resist the escape of the food ; but, from the absence of a true sphincter, to a much less degree than the pylorus. It is im possible that, under these circumstances, there could be any reflex action, as the stornach is removed from its connection with the nervous centre. The valvula col' appears to act simply on mechanical principles.
' There is, I apprehend, no more evidence of the exclusively reflex nature of the acts of expulsion than of that of the acts of retention. The expulsion of the fxces and that of the urine are voluntary acts, aided essentially by the con tractile power of the muscular fibres of each vis cus, and perhaps, under peculiar circumstances, by a physical excitant. Were this power reflex, the expulsion would be no doubt much more frequent and much less under control, and, therefore, productive of frequent serious incon venience. The expulsion of perspiration is probably effdcted by the simplest mechanical means, the newly secreted fluid pushing, before it that which was previously formed. The expulsion of the semen does, indeed, exhibit the characters of a true reflex act ; but here how rnarked is the physical stimulus, and how necessary that it should reach a certain point of excitement before the action of expulsion re sponds to itl• As to the expulsion of the fcetus in parturition, while I am willing to admit that the physical power of the cord excited by the sensitive nerves at the neck of the uterus may exercise some influence on the contrae tions of the uterus, it seetns to me quite evi dent that the actions of this organ are reflex only to a very slight deg,ree. In the first place, anatomy teaches us that the muscular parts of the uterus have a very trifling connexion with the spinal cord ; the nerves distributed to it being few, and these only partially derived from the spinal cord. Secondly, parturition may take place even when the spinal cord has been diseased or divided so as to cut off its in fluence upon the inferior half of the body. Thirdly, it has lately been ascertained that in women under the influence of ether, the act of parturition may take place with vigour, although the nervous power have been very considerably depressed by the influence of that agent.