tendons is not necessary for their production; the one condition which all have in common is that passive tension is essential for their occur. rence, and I have suggested that they be termed myotatic contractions (Tarikos, extended). The irritability, on which they depend, is due to and demonstrative of a muscle-reflex action which depends on the spinal cord. It is highly probable, as Tschirjew suggested, that the condition on which the myotatic irritability depends, is identical with muscular "tone." Since the experiments of Heidenhain, it has been generally admitted that "tone" depends on tension, and is a reflex process.†

A true "tendon-reflex" may be excited by pinching the tendon, but this is a start of the whole limb, precisely such as results from a pinch of the skin. It is an instance of the pain-reflex described above. The importance of discarding the tendon-reflex theory (and the name that must always involve it to those who have not studied the matter) is very great, for it prevents the comprehension of the true nature of other phenomena of great importance.

Paradoxical Muscular Contraction.-This name has been given by Westphal to a slow tonic contraction occurring in a muscle when its attachments are suddenly brought nearer. It is best seen in the tibialis anticus; if the foot is grasped, and passively flexed on the leg, the tibialis anticus contracts, sometimes after an appreciable interval; its tendon stands out, and the contraction keeps the foot flexed for a time which may be some minutes (in one case for twenty-seven); the relaxation is slow. Repetition lessens the contraction. The contraction is not voluntary (although a voluntary contraction may simulate it). It may occur on one side only. The contraction produced by brief faradism may be similarly prolonged in the same case. A similar contraction may be observed in the extensors of the toes, sometimes in the flexors of the knee, rarely in the arm muscles. Its mechanism is uncertain; whether reflex or not, whether produced through the muscle itself, or through the tension on the antagonists, (as Erlenmeyer has maintained), we do not know. It seems to be an excess of the contraction by which a muscle adapts itself to passive shortening of its course. In the cases that have presented this phenomenon there has been no muscular rigidity, and no great excess (even sometimes a loss) of the myotatic irritability. This adaptation to posture seems a phenomena quite separate from that which underlies myotatic irritability. It may occur in the early stage of tabes, and in some other affections, but its significance is not known. A phenomenon somewhat similar occurs in hysteria (Féré); it is indeed but an isolated and imperfect instance of the condition that

Diagnosis of Diseases of the Spinal Cord,' 2nd edit., 1881, p. 29.

By some interesting researches recently published, Mommsen has reached the same conclusion, that muscular tone is dependent on a muscle-reflex action excited by tension acting on the sensory muscle-nerves (Virchow's Archiv,' Bd. 110, p. 22).

Arch. f. Psych.,' Bd. x, p. 243.

when universal and perfect, constitutes the filexibilitas cerea of catalepsy. The nature of these contractions will be considered further on.

CHANGES IN NUTRITION.-The nutrition of the tissue-elements is largely under the influence of the nervous system. Whether this influence is exerted through special "trophic" nerves, or through the motor, the sensory, and especially through the vasomotor nerves, is a question that has been much discussed and is still undecided. The balance of evidence is against the existence of special trophic nerves. The fact regarding these changes that is surest and most important, is that acute disturbance of nutrition is the result of irritation of the nerve-trunks and centres, and is in proportion to the intensity of that irritation. If a thread is passed through each sciatic nerve, and one is also irritated by the application from time to time of irritant liquids, trophic changes occur in that limb with greater rapidity, and far greater intensity, than in the other (Lewaschew).

The same fact is frequently indicated by the extreme readiness with which trophic lesions of the skin and even cellular tissue, occur in certain forms of inflammation of the spinal cord especially in those that have a strong tendency to spread in the cord, and hence may be regarded as possessing more of this peculiar quality that, in our ignorance, we term irritative. One theory and one only seems to explain all the facts. It is that the nerve-endings have a structural continuity with the tissues,-are related to them in a sort of molecular contact similar to that which exists in the tissues themselves-and that the nutrition of the molecules of the tissues is determined in its character by that of the nerves. The process of irritation descends the nerves, it passes from them to the tissues and invades them all. Thus we can understand equally the acute changes in the muscles which will be described, and also those in the skin and other tissues which are under the influence of the sensory fibres.

Nutritive changes in the skin are easily recognised, but they differ much in their character according to their acuteness. When they are rapid, and due to very acute irritation of the nerves or the spinal cord, such as those just mentioned, the temperature of the limb is raised, the vessels readily dilate, and remain dilated for a long time, bula form, containing a dark-coloured liquid, and slight pressure occasions a slough. These changes sometimes occur spontaneously, but are more often excited by some cutaneous irritation, and very slight irritation of the skin will suffice to produce them. Trifling pressure will set up a slough, and extensive vesication may result from the application of a hot-water bottle that is not more than pleasantly warm to a healthy hand. When the nerve irritation is intense, effusion may occur into the joints.

In the case of the fifth nerve, acute trophic changes occur in the

.

eyeball chiefly when the disease involves the Gasserian ganglion, or the nerve in front of it. To produce the same effect, a lesion behind the ganglion has to be more irritating than one in front of it, and it is probable that a similar relation obtains in the case of the spinal nerves and the spinal ganglia. Very intense changes in nutrition are, however, common in acute inflammation of the spinal cord.

The alterations in nutrition in chronic lesions (which have been carefully studied by Paget and Weir Mitchell) differ considerably from those that result from acute irritation. There is a slow change in the nutrition of the skin, which becomes red, thin, and shiny-the "glossy skin" of Paget. The subcutaneous tissue also wastes, so that the finger tips become pointed. The growth of the hair and nails is retarded, and the latter become brittle. The bones may suffer in their nutrition, and may break more easily than in health. If the lesion occurs during the period of growth, this is retarded. These changes seem to depend on an altered life tendency of tissue elements that have been formed without some influence received from the nerves.

The muscles suffer from lesions of the motor nerves; the minute changes are described at p. 53. At first there may be merely flabbiness, and an appearance of wasting that is not confirmed by measurement, but there is soon an actual diminution in the circumference of the limb. In extreme cases all the muscular tissue disappears, and the contour of the limb is considerably changed. In comparing the size of the limbs on the two sides, it should be remembered that the limbs on the right side are normally somewhat larger than those on the left side, and that the difference varies according to the occupation of the individual, and the extent to which this involves an excessive use of the limbs on one side. In measuring, great care is necessary to secure, as nearly as possible, the same conditions on each side, both as regards the state of the muscles and the place of measurement. It is best, wherever possible, to take the maximum measurement in each part, rather than to attempt to make the measurement in the same place. In the calf, the maximum circumference should always be taken. In the thigh. accurate measurement is extremely difficult, because a maximum cannot be taken. We may endeavour to measure at the same point in the thigh, at the same distance from the condyle, but it is very difficult to be exact, and a more accurate comparison can often be made by taking the minimum circumference above the knee, in spite of the fact that the muscular tissue there is small, and the difference less than it is elsewhere. In the forearm the best result is obtained by taking the maximum measurement around the muscular prominence below the elbow, over the supinator longus. If the upper arm, the circumference is nearly the same in the middle third, and the middle of the humerus may be measured, with little risk of error. In all cases care must be taken to draw the tape equally tight at each place. It is easier to do this with a flexible steel measure than with an ordinary tape measure. Exactness in this respect is best secured by having a

spring at one extremity of the tape, with an index that will show the tension, which can thus be kept the same at each place.*

ELECTRICAL IRRITABILITY.-The nerves and muscles are excitable by electricity, and the excitability is changed by disease, of which the change is often an important symptom. It indicates the state of nutrition of the nerve-fibres and muscles, and from this we can often draw important inferences regarding the condition of the centres. An outline of the most important facts regarding electricity in its application to medicine, is given in the Appendix, but it may be well to mention here the chief facts of diagnostic importance.

In the normal state, nerve-fibres are stimulated by either the induced or the voltaic current, the stimulation of the motor nerves being shown by contraction in the muscles supplied by them, that of the sensory nerves by the sensation that is caused. The contraction of the muscles is continuous when the faradic current is applied, but if the isolated shocks of which the current consists are separately passed, each causes a brief, momentary contraction. When the voltaic current is applied, contraction occurs, with a current of moderate strength, only when the strength of the current is changed, and chiefly when the current commences or ceases to pass, i. e. when the circuit is "inade" or "broken." The stimulation of the sensory nerves is greatest at those times, but occur also, in a much slighter degree, during the whole time that the voltaic current is passing. Hence this is probably the case also in the motor nerves, although the stimulation is too feeble to produce a contraction in health with a strength of current that can be borne. In proportion as the nutrition of the nerve-fibres is impaired, their excitability is lowered and a stronger current of each kind is required to excite them and cause contraction in the muscles they supply. When their nutrition is much impaired-i. e. when the fibres are 66 degenerated "no contraction can be obtained even with the strongest currents.

The changes in the excitability of the muscles are less simple, because in them there are two excitable structures-the terminations of the nerves, and the muscular fibres themselves. Of these the nervefibres are the more sensitive to faradism, and the faradic stimulation of a muscle under normal circumstances is by means of these motor nerve-endings. Thus we find that its excitability corresponds in degree to that of the motor nerve supplying it. The muscular fibres themselves are, even in the normal state, less sensitive to faradism than the nerve, apparently because they are incapable of ready response to a stimulus so very short in duration as are the shocks of which the

As in an instrument contrived by Dr. Russell Reynolds (and made by Hawksley) in which two rods, to be placed along the middle, one of the thigh, the other of the leg, are joined by a hinge that can be tightened at any angle, and on the upper one is a tape with the contrivance mentioned in the text. An analogous and most convenient tape measure.

faradic current consists.

(The proof of this consists in the fact that under the influence of curara, which removes the excitability of the terminations of the motor nerve, the muscle requires a stronger faradic current to stimulate it than in the normal state.) But when the nerve is degenerated the slowly interrupted voltaic current stimulates the muscle as readily as in the normal state; a contraction occurs when the circuit is completed or broken-distinctly slower than that which occurs when the nerve-fibres are intact, and due to the stimulation of the protoplasm of the muscular fibres themselves. The fact that, under normal circumstances, the contraction which is caused by the voltaic current is as quick as that produced by the faradic shock, is ground for believing that, in health, the voltaic, as well as the faradic current, causes the muscle to contract chiefly by exciting the motor nerve-endings When the motor nerve is degenerated, and will not respond to faradic or voltaic stimulation, the muscle also loses all its power of response to the former. Apparently the nerve-degeneration is accompanied by changes in the nutrition of the muscular fibre, by which any power of response to faradism, which it possessed in the normal state, is lost. But the response to the voltaic current remains, and becomes quickly more ready than in health, doubtless in consequence of nutritive changes which develope what the older pathologists called, truly enough, "irritable weakness." Moreover, there may commonly be observed a change in the readiness of response to a certain mode of stimulation with voltaism-a "qualitative" change, as it is termed. In health, the first contraction to occur, on gradually increasing the strength of the current, is at the negative pole when the circuit is closed, and a stronger current is required before closure-contraction occurs at the positive pole. But, in the morbid state we are discussing, closure-contraction may occur at the positive pole as readily as at the negative, or even more readily -and contractions, when the circuit is broken, occur far more readily than in the normal state. This condition, then-faradic irritability lost, voltaic irritability increased and often changed in quality-is termed the "degenerative reaction," because it occurs when the nerve-fibres are degenerated; and if we test them we shall find no response to any stimulus, voltaic or faradic. It occurs when the nerves are separated partially or completely from their motor nervecells, and if no such separation exists, it indicates an acute degenerative change in those nerve-cells.

But the motor nerve-cells and fibres often undergo changes in nutrition of a much more chronic character. In this condition the irritability of the fibres is lessened gradually and slowly. The irritability of the intramuscular nerve-endings is lessened in the same degree as that of the nerve-trunks, and we have a diminution to both faradism and voltaism. The nutrition of the muscular fibres is slowly, gradually, impaired; and when the nerve-fibres are much affected the muscular fibres are also. There is no stage in which the