the contraction of the foot-muscles (plantar reflex) through the lower part of the lumbar enlargement of the cord; the skin of the buttock calls into action the glutei muscles (gluteal reflex) through a segment which corresponds to the escape of the fourth or fifth lumbar nerve; the skin upon the inner aspect of the thigh causes the cremaster muscle to draw the corresponding testicle toward the external abdominal ring (cremaster reflex) by influencing the cord at the level of the first or second lumbar nerve; the skin upon the side of the abdomen creates reflex movements of the abdominal muscles (abdominal reflex) by affecting a segment of the cord situated between the levels of the eighth and twelfth dorsal nerves; the skin upon the side of the chest creates a reflex response in the region of the epigastrium (epigastric reflex), which depends upon a spinal segment extending from the fourth to the seventh dorsal nerves; finally, the skin between the shoulder-blades causes the posterior axillary fold or the teresmajor muscle to contract (scapular reflex) by influencing the spinal segment between the levels of the fifth cervical and third dorsal nerves.

"By means of these reflexes, we are enabled to test the various spinal segments from the neck to the terminal extremity of the cord. Should any be found to be absent, it should be remembered: (1) that the reflex excitability of the cord varies with individuals and is always greater in youth than in old age; (2) that the plantar, cremasteric, abdominal, and epigastric reflexes are variable in health, but are more constant than the scapular; (3) that cerebral lesions may impair them on the side of the hemiplegia, for reasons not as yet well understood; and (4) that systematic lesions of Burdach's or Goll's columns tend to diminish or abolish them.

"The DEEP' or 'TENDON REFLEXES' are also of great value as a means of determining the condition of excitability of different segments of the cord. The ones now commonly employed are called the foot-clonus'; the 'knee-jerk' or 'patella reflex'; the 'peroneal reflex'; and the 'tendo

THE VARIOUS TENDON REFLEXES.

597

Achillis reflex.' The method of obtaining these reflexes in the most satisfactory manner will be described separately. It is important, however, to remember one fact in connection with them before deciding as to their clinical significance, viz., that the reflexes should be tested upon both sides and compared with each other, because any perceptible differences between the two sides is a probable indication of some pathological lesion of the cord.

"The knee-jerk has for years been recognized and employed by Charcot in diagnosis, although it was first systematically investigated as a clinical symptom by Westphal and Erb. Gowers remarks in a late work, 'It is not a little curious that this knee-jerk, which for generations has amused school-boys, should have become an important clinical symptom.'

"To properly test this reflex movement of the limb, the muscles of the quadriceps extensor tendon must be put upon the stretch to a moderate degree, and the leg be unrestricted in its ability to respond. The common method employed is to have the patient cross the leg over the knee and allow it to hang passively at an angle which is nearly ninety degrees. Perhaps a still better way is that employed by Gowers, viz., to allow it to hang over the forearm of the physician when his hand is placed upon the opposite knee of the patient, because in this way the jerk is often elicited in stout people when it otherwise fails. The space between the patella and the tibia is then struck with a percussion-hammer or the side of the physician's hand upon the bare skin with sufficient force to slightly increase the state of muscular tension which has resulted from flexion of the leg. This will cause a reflex contraction of the quadriceps extensor muscle, and the foot will be jerked upward without the volition of the patient as a factor in the movement. In about two per cent of healthy subjects, the knee-jerk may be found to be totally absent, in spite of all possible care in employing the test. This fact is important, since the absence of the knee-jerk is too often construed as a positive sign of spinal disease.

"The ankle-jerk. If the muscles of the tendo Achillis be put upon the stretch by flexion of the foot, a blow upon that tendon will cause a similar extension of the foot.

"The foot-clonus. When the excitability of the cord is excessive, if the foot be firmly flexed and held so by the pressure of the hand against the sole, a series of rhythmical reflex movements of extension follows, which vary between six and ten per second. They can be traced upon a revolving drum by attaching a pencil to the foot, as easily as a sphygmographic tracing is made. This clonus is more apparent when the knee is firmly extended than when flexed.

"The peroneal reflex. The tendons of the peroneal muscles pass to the bones of the foot at the outer side of the ankle. A blow made upon them when the foot is bent inward, to produce a moderate degree of tension of these muscles, will elicit a reflex movement, as in the case of the patella tendon.

"The front-tap contraction.' Gowers has described a reflex test for increased spinal irritability that he considers particularly delicate. It consists in flexing the foot with the hand upon the sole, the knee being extended, and applying the blow to the muscles on the anterior aspect of the leg. It is followed by a reflex contraction of the muscles of the tendo Achillis which are not directly affected by the blow.

"Although the deep reflexes are commonly tested only in the lower extremities, the same phenomena may be elicited in the triceps or biceps muscle of the arm as in those of the thigh and calf, if subjected to the necessary position to insure tension of the muscles before the tap is given over the tendon."

Before we leave the subject of the spinal cord and its architecture, it may be well to consider some of the bearings which anatomy and physiology have upon the clinical recognition of disease confined to this wonderful piece of mechanism.

The hints which are thrown out in the remaining pages of this section must of necessity be crude and incomplete.

KINESODIC AND ESTHESODIC SYSTEMS.

599

CLINICAL POINTS PERTAINING TO THE SPINAL CORD.

From the physiological experiments as to the functions of the different columns of the cord, it now seems possible to divide the spinal cord into two great subdivisions, which will be of interest from a purely clinical standpoint, as well as from a physiological aspect. The first of these includes both pyramidal columns and the anterior horns of the gray matter, and is the probable path of all motor impulses which traverse the cord, as well as the seat of "trophic influences" upon tissues. The latter includes the posterior and cerebellar columns and the posterior horns, and is the probable path of sensory impulses, while it also is associated with the function of coördination of movement. Now, both of these subdivisions include several parts of the spinal cord, which have been separately named in previous pages; hence, the term "system" is applied to both, the former being named the "kinesodic system," and the latter the "æsthesodic system." These names will be constantly used, therefore, when the portions of the cord which convey either motor or sensory impulses are spoken of as a whole; while the other names applied to special portions of the cord will chiefly be used in defining the situations of special lesions whose symptomatology may be under discussion.

If we are to attempt to grasp the symptoms by which the various lesions of the spinal cord may be recognized during life, and to understand why certain effects must be produced (when the situation of the lesion is known to us), we must make some classification of the diseases which affect the spinal cord on such an anatomical and physiological basis as shall naturally tend toward the constant application of these branches of medical science to the symptoms presented by the patient. It has been customary with most of the late authors upon the special subject of nervous affections to consider the diseases of the motor regions and of the sensory regions of the cord separately; using the term "systematic

lesions" to express the fact that all of those diseases, which are not purely local, affect either the kinesodic or æsthesodic systems. When we speak of systematic lesions, therefore, we mean those types of disease which tend to diffuse themselves, for a greater or less extent, upward and downward, without extension to the adjacent columns; thus the columns of Goll and of Burdach may be involved in the æsthesodic system, the lateral columns and the columns of Türck may be involved in the kinesodic system, while the anterior or posterior horns or central part of the gray matter may be the seat of disease, irrespective of the other parts of the cord.

In contradistinction to the systematic lesions, certain types of disease tend to spread laterally, and thus to involve different columns of the cord in succession. These are grouped under the general head of "focal lesions" or "non-systematic lesions." In this form of degeneration, or of new tissue development, the extension is usually limited in a vertical direction, but it may extend, laterally, not only to diverse columns, but may even involve both the kinesodic and æsthesodic systems in its progress.

It will exceed the proper scope of the course of lectures which I have prepared for this winter, to enter into a full description of the symptoms of all of the diseases of the spinal cord; but it is important that you start with a general classification of the diseases which may affect this region, in order that you may properly understand the meaning of terms which you will find growing into use with astonishing rapidity. It is also to be remembered that the classification which I have given you is based on anatomy and pathology, and may differ markedly from those of some authors with which you may be familiar; a little study will, however, remove all confusion, and perhaps add to your more perfect comprehension of the subject.