Last year, when treating upon the question of rigor mortis, I drew the attention of the Section to a form of muscular contraction induced in coldbloods by the irritant action of such vapours as ether, chloroform, bisulphuret of carbon, amylene, &c. I pointed out that they were the most extreme forms of contraction of which these muscles were capable. The persistent, in most cases permanent character of the contraction at once associated it with the forms of tetanus induced by water of certain temperatures and by the discharge from Ruhmkorff's coil. The extreme delicacy of this mode of exciting muscular contraction by ethereal vapours has enabled me to perform some very interesting and instructive experiments.

I have succeeded in proving, by experiments in which the nervous system has, as far as possible, been removed, and, better still, by experiments on isolated muscles, (1) that both chloroform and warm water act directly upon and produce universal contraction of the muscular tissue, which, according to the circumstances of its induction, may or may not be permanent; (2) that when the nervous and vascular systems are present they complicate the result, and furnish us with illustrations of most important physiological principles.

Taking first THERMAL TETANUS, I find two normal limbs (i. e. supplied with both blood and nerve-influence) contract simultaneously. Two limbs deprived of both blood and nerve-influence also contract simultaneously. Of two limbs, the one having neither nerve nor blood, and the other both nerve and blood, the latter contracts first. Of two limbs, the one having neither nerve nor blood, and the other blood only, the former contracts first. In CHLOROFORM TETANUS the same holds good as in the first two examples of thermal tetanus; but of two limbs, the one having neither blood nor nerve, and the other having both blood and nerve, the former contracts first. Of two limbs, the one having neither blood nor nerve, and the other nerve but no blood, the latter contracts first.

An analysis of these various results shows that both warm water and chloroform exercise an excitant action upon the nervous system of the frog, which tends in both cases in the direction of muscular contraction, but which of itself alone is too weak to bring about such an affection of muscle, and, further, that the warm water is more powerful in this respect than the chloroform. It also affords evidence of the important principle, that certain elements of the blood in the interstices of the muscular tissue oppose a powerful obstacle to such agencies as tend to throw muscular tissue into a state of contraction.

Muscle when dynamically perfect is related, on the one hand, to certain stimuli, as nerve and external agents, which tend to induce contraction, and, on the other, to some of the elements of blood, which bring about its elongation; but its degree of proneness to fall into contraction appears to be directly proportionate to the amount of force generated in it by the blood-in other words, to its irritability; and although the galvanometric evidences of the existence of force are masked during contraction by the derived electromotor currents taking on the negative variation, yet this by no means proves (as some suppose) that the blood-generated forces are absent; for we have previously seen in explaining Sequard's experiment that the contractive energy, i. e. the tendency of the molecules of muscles to approach each other, may be increased two-and-a-half times, which is at once proof that they do not approach by virtue of any permanent force which they possess as mere physical atoms; for such force would be a fixed and not a varying quantity. It is evident therefore that both the power of contraction and of elongation is derived from the blood, and not the elongating force alone; and we must

not, with Dr. Radcliffe, fall into the error of considering that muscle necessarily passes into a state of contraction in the absence of an elongating force; for experiment shows that the most perfectly relaxed state of muscle is compatible with the absence of every trace of irritability.

I shall now proceed to narrate several experiments in which the relation which blood bears to muscular tissue is more fully displayed, and by which it is made evident that the blood gives the power by which the elongated or relaxed state of muscle is maintained.

Exp. 1.-A frog is moderately chloroformed; when removed from the vapour, particular note is made that the limbs are perfectly flaccid or relaxed, and that the heart is beating. The heart is now exposed and excised, and in a few seconds or minutes, according to the amount of chloroform imbibed by the tissues, the limbs will spontaneously extend and become rigidly tetanic.

Another frog was slightly chloroformed, and the observation made that the heart was still acting, and that the whole of the muscles were quite flaccid. The structures of one thigh were then cut through to the bone, so as to sever all nervous and vascular connexions. The muscles of this limb gradually commenced to contract, and in a few minutes the leg and foot were extended and the webs stretched out. The muscles of the other limb and the trunk generally remained in a completely relaxed state. After the lapse of some minutes I observed a tendency in the unmutilated limb to extend, and in the fore feet to approach the central line of the body, and to clasp, as in tetanus of the male frog. Directing my attention to the heart, I could not detect any pulsation, and I therefore removed the parietes of the chest; the access of air reexcited the action of the heart, and very quickly the muscles of the unmutilated limb and general trunk became again flaccid. The heart again losing power, the condition of contraction a second time came on, and gradually became more and more complete. On reexamining this frog after the lapse of an hour, I found that the muscles had again become flaccid this time not only in the unmutilated limb, fore feet, and muscles of the trunk, but also in the limb which, as far as its soft parts were concerned, was completely amputated. Not the slightest trace of irritability, however, was now detectable. Nothing could be plainer than the teaching of this experiment. The muscular tissue was subjected to a dual influence :— first, the chloroform tending to excite it to contract; secondly, the blood, or certain of its elements, tending to maintain it in the relaxed or elongated state; and accordingly as one or other of these influences prevailed, the muscles became alternately contracted or relaxed. After the cessation of the circulation the antagonism was feebly continued between the evaporating traces of the chloroform on the one hand, and the interstitial juices of the muscle on the other, the balance of power being so nicely adjusted that the interstitial nutrition was just capable of restoring the relaxed condition, but incapable of conferring the slightest degree of irritability upon the muscles. It is rarely that we obtain this exact balance of the influences; for if the amount of chloroform in the muscles is too large, the condition of permanent contraction obtains; and if too small, there are slight evidences of returning irritability after the muscle has become elongated.

Another satisfactory mode of exhibiting this function of the blood is to compress the abdominal aorta of a frog, and, having ascertained by the microscope that the circulation in the lower limbs is securely arrested, oil all parts of the body, with the exception of one limb, expose this to the vapour of chloroform, protecting as much as possible all other portions of the body from its influence. This limb will after a time show a disposition to con

tract. It should then be removed from the vapour; and when it has become fully extended, the tourniquet should be taken off; the blood will then gradually find its way into the limb, and restore the flaccid elongated condition.

In this experiment we have the contrast of two limbs without blood, one of which is under a contracting influence; and we get an excess of chloroform in the tissues of one limb and protect the animal to a great extent from being generally affected. As might be expected, this state of contraction is never so easy to produce when an animal possesses its full complement of blood; for although the blood may be stagnant in the vessels, it will supply for a considerable time the elements which oppose the contracting-powers of the chloroform; hence, if we would produce the state of contraction under such conditions, an amount of chloroform is demanded in the tissues which ordinarily destroys the animal. But by adopting the plan of allowing the ingress of the chloroform only through the limb which we wish to affect, we overcome this obstacle and retain the heart in such a condition that the circulation can be restored and the contractive state dissipated when the mechanical impediment is removed from the aorta.

In concluding this paper, I propose to take a hasty survey of the various affections of muscular tissue as they have presented themselves in my experiments.

Let us take as an illustration the gastrocnemius muscle of the frog in the elongated or uncontracted state. 1. It may exist in this elongated or uncontracted state with all its dynamical powers in a state of integrity. This is its normal condition, as we see it in the absence of stimuli. 2. It may exist in this state when deprived of dynamical power, or, in other words, in the absence of irritability. 3. Both these conditions of elongation may be associated with softness or flaccidity of the muscular structure, the former necessarily so; the latter not, as the fixity of rigor may prevail.

Now let us take the same muscle in a state of complete contraction. 1. It may exist in this state of contraction with its dynamical powers perfect. This is true in those normal contractions which quickly give place to relaxation. 2. It may exist in this state when deprived of dynamical power, as seen in the forms of permanent contraction induced by warm water and ethereal vapours. 3. In a state of softness, or in a hard coagulated state. The soft state is represented by normally contracted muscle, severed from one of its attachments. The hard state is induced by ethereal vapours and extremes of temperature.

As with the state of elongation, so with that of contraction, the truly dynamical state is one of softness.

The dynamical conditions on which irritability depends may therefore exist both in the elongated and in the contracted state, and may also be nonexistent in both of these states. Properly speaking, irritability is no more the tendency which a muscle exhibits to contract than the disposition it shows to relax or elongate subsequently to contraction; in fact a comprehensive definition must include both these conditions. Nor is either of these states to be regarded (as far as muscle alone is concerned) as conditions of rest; for they are both active states so long as the muscle is a vital structure, and both inactive when the dynamical power of muscle are absent.

As yet there seems to be no reliable experimental evidence to show that muscle per se ever contracts spontaneously, i. e. in the absence of a stimulus; but there are plenty of indications that the same agent is a greater stimulus at one time than another; nor is there any evidence to show that muscle

will contract on the withdrawal of elongating influences, but abundance to the contrary in the fact that it will remain in the elongated state in the absence of all susceptibility. Contraction and elongation would seem both to be dependent on the existence of polar forces, which have a certain relation, on the one hand, to excited nerve and external stimuli, and, on the other, to some of the elements of the blood,-excited nerve and external stimuli inducing the attractive, which involves contraction, and the blood the repulsive polar attitude essential to elongation.

The attractive state of the muscular molecules which represents contraction, is the condition in which force is exhausted by the association of unlike polarities; while the state of elongation being that in which every molecule is opposed to every other, force may be accumulated. In proportion to the amount of force accumulated in the molecules will be the intensity of their contractive or elongative energy; and also in proportion to their charge will be their proclivity to disturbance-in other words, their susceptibility to stimuli.

When a stimulus can no longer act, it is because the force is exhausted. If the chemistry of the muscle be not absolutely arrested, the power to contract under a stimulus will return. If at the moment of its action a stimulus be so excessive as to induce the attractive state of the molecules, and at the same time to destroy the force-producing powers of the muscle, the molecules will remain in the state of approximation, simply because there is an absence of any power to rearrange them. Conversely, if the forceproducing powers be destroyed during the state of elongation, the molecules remain apart.

Muscle, therefore, as a dead structure, has no tendency to remain in either one or other of these states preferentially. The loss of irritability is the first evidence we possess of a series of chemical changes which culminate in such a coagulation of the muscular juices as to cause fixity, or setting of the muscle. When these changes take place in the elongated muscle, the fixed condition is produced which we recognize as rigor mortis; when, on the other hand, they take place in the contracted muscle, they induce the fixed hard condition of the muscular structure seen in ethereal and thermal contractions.

Substances which affect muscular tissue may be classified as pure stimulants, stimulo-coagulants, and depresso-coagulants. All substances possessing the coagulant property arrest the chemical reactions between the muscular tissue and the blood, by which the fluid on which irritability depends is generated. The stimulo-coagulant class is represented by the irritant action of chloroform and the ethers generally, and by extremes of temperature; the depresso-coagulant by chlorine, carbonic acid gas, and the sedative action of very dilute ether-vapour.

It is possible, therefore, to have rigor mortis, or coagulative setting, in both elongated and contracted muscles.

While, therefore, my researches contradict the theory which refers the phenomena of living muscle to statical electricity as an elongating power simply, contraction being regarded as due to an inherent attractive power of the muscular molecules, they are singularly in accordance with the conclusions of Du Bois Reymond, who regards every elemental part of muscle as a centre of electromotor action, containing within itself positive and negative elements, arranged in a dipolar series,-and seem to fill up a gap, by showing that the repulsive attitude of this series is maintained by the blood.

Report on the Physiological Action of certain Compounds of Amyl and Ethyl. By BENJAMIN W. RICHARDSON, M.A., M.D., F.R.S. In two previous Reports to the Association, I dwelt especially on the action of certain of the compounds of amyl. The first Report dealt exclusively with the substance known as the nitrite of amyl. The second Report had further reference to the same body, and also to amylene, amylic alcohol, and the acetate and iodide of amyl. In some degree these Reports were complete as far as they went; that is to say, the facts presented were sufficient to demonstrate what visible physical influences were exerted on dead and on living matter by these representatives of the amyl series; and as I carefully separated the facts from the speculations that were fairly to be founded on them, the Association expressed its satisfaction by requesting me to continue researches in the same direction but with a wider object. I was desired in the next Report to repeat what might require repetition, but specially to pay attention to the ethyl-compounds, with a view to determine, if that were possible, whether there was any analogy in physiological action between the analogous compounds of the two series.

SUMMARY OF PAST RESEARCHES.

Before I enter on new ground, it will be advisable for me to recall the main facts described in previous years and bearing on the amyl series.

1. It was shown that the nitrite of amyl when inhaled was the most powerful excitant of the circulation at the time known. It was demonstrated that during such inhalation the action of the heart was doubled in rapidity in thirty seconds, in men and warm-blooded animals: further, it was proved that this intense action was immediately followed by deep suffusion of the skin, by breathlessness like that produced by running, by a peculiar sensation of fulness and throbbing in the head, and ultimately by failure of muscular power of the extremest kind. It was also proved that there was no destruction of the nervous sensibility, that in animals there was an obvious expression of sensibility up to the moment of death. Lastly, it was shown that in cold-blooded animals, such as frogs, the nitrite of amyl suspended animation for hours, and even days,-and that, in young warm-blooded animals, after exposure to it until they seemed to be dead, the action of the heart continued for so long a period as eighteen hours.

2. In respect to amylene, it was shown that the vapour of it was antiseptic, even when freely admixed with air; physiologically tested on living animals, it is found to be capable of administration by being inhaled. It does not provoke local irritation, but it rapidly produces collapse and total insensibility to pain. At the same time it seems to interfere less with consciousness than other narcotic vapours. This fact is of peculiar interest, because the apparent consciousness exhibited by the subject is not shared in by himself, it is an objective, not a subjective phenomenon. The person under the influence of the vapour may perform acts which have all the semblance of conscious acts; but when he recovers he has no recollection of anything that has occurred. The state thus induced is very much like the phenomenon of somnambulism; and I ventured to suggest that in this experiment we had a key to the cause of the disease somnambulism, viz. that there was possibly formed in the body of the somnambulist, by a faulty digestion, a substance of similar action to an amyl-compound. Amylene I showed was a good anesthetic, and many surgical operations have been performed under its in