would, when strongly flexed, present a continuous flat surface on which the weight of the fore limb could rest. Add to this, that the dorsal aspect of the claws had the appearance of having been used in this way. Having observed these points as likely to account for the actual position of the fore feet in our specimen, I was struck with Prof. Hyrtl's description of the muscular structure of the palm-the more so as he does not suspect the mode of progression to be different to that of D. gymnurus, with which he compares it. When describing the flexor muscles of the fore limb, he thus expresses them: "A singular union characterizes the flexorial province of the muscles of the forearm and hand, whose number is less than usual from the absence of the flexor longus pollicis and pronator quadratus, but whose fleshy belly presents so large a mass as to strike one with admiration. With so rich an apparatus of muscles has the sagacity of nature provided for the flexion of the hand and fingers-strength being combined with celerity of action—that the prompt flexion of these may occur at the same moment, and with the same effort as extends the forearm......These muscles have a common fleshy origin, consisting of three layers. The superficial layer yields to the rest in volume, and divides into four tendons, of which the first, second and fourth resemble in their course and mode of insertion the pronator teres, and the radial and ulnar flexors of the carpus respectively. Concerning the third there appears some doubt. From its origin, course, and aponeurotic expansion you would take it for a palmaris longus. But when its palmar aponeurosis splits up into four flat tendons, which go to the first phalanges of the fingers (the pollex excepted), and there, by a forked division, give passage to flexor tendons which are produced to the last phalanges, the obvious suspicion is that you have to do with a flexor digitorum sublimis. I myself adopt the former view, and for the following reasons. Firstly, because the so-called flexor sublimis constitutes the mass of the second muscular layer. Secondly, because the common rule among mammals demands that the bifid tendons of the fl. sublimis should be inserted, not into the base of the first, but into the sides of the second internode. Thirdly, it is evident from an accurate examination of their insertion, that the tendons of which we speak are not perforated, but are 16 MR ATKINSON. OSTEOLOGY OF THE PICHICIÉGO. so blended with the fibrous sheath which guards the flexor tendons as would require even in the human hand a most subtle preparation to demonstrate. We therefore declare this ambiguous muscle to be the palmaris longus. Its tendon where it crosses the carpus contains a minute lenticular ossicle." Hence, I think it will be clear that the unusual development of this muscle and its aponeurosis in Chlamydophorus is specially provided for fixing the palm in the flexed position, and thus enabling the animal to walk on the dorsum of its outer toes while at the same time this attitude of the limb appears the best adapted for scooping out and throwing backwards the sand in which it burrows. I am indebted to the valuable assistance of my friend, Mr James Walker, who has kindly prepared the drawings which accompany this paper. DESCRIPTION OF PLATE. Fig. 1. Skeleton of Chlamydophorus truncatus (nat. size). The fulcra supplied by the ischium are best seen in this figure. Fig. 2. Sphæroma ischii and tail, viewed from behind (nat. size). Fig. 3. Pelvis and sphæroma viewed from above and in front, so as to shew the fulcra supplied by the sacrum and the 'ascending processes. Fig. 4. The Sternum, clavicles, and first pair of ribs (nat. size). I regret to find that, in the transference to the stone by the lithographer whom I employed, the drawing of the teeth has been altered so that they all appear level-topped. Unfortunately this was not discovered till it was too late to be rectified.-ED. ON CARDIOGRAPH TRACINGS FROM THE HUMAN CHEST-WALL. BY A. H. GARROD, St John's College, Cambridge. ON applying the hand over the left pectoral region the movements of the heart can be felt with facility, especially at the end of expiration. In the following paper an attempt is made to classify and partly explain these movements, as they are reproduced by the sphygmograph. The earliest and perhaps the only published observations on these curves are by Dr Marey of Paris', who gives one trace from the human subject and others from the horse, which latter have the advantage of being associated with synchronous traces from the interior of the ventricle and of the auricle. No previous observations can be found as to the relative duration of the different elements of and the other peculiarities in the human heart apex traces at different rapidities of pulse. While the subject is sitting or standing the sphygmograph can be made to give a very perfect record of the heart's movements, as they are transmitted to the intercostal tissues, by holding the instrument horizontally with the watchwork to the right hand, the plane of the recording paper and consequently of the whole instrument being parallel to the floor, and the lever-pad at or near the point of maximum pulsation, between the fifth and sixth ribs. While lying, the instrument must be held upright, as when wrist traces are taken. The movements of respiration cause so much irregularity in these traces, that it is advisable to stop breathing while they are being taken; and this should be done at or near the end of a normal expiration; it is then found that little or no effect is produced on the heart's action, during the short time, about seven seconds, that the instrument is applied. It will also be found that quick pulses are more easily taken than slow ones, because the heart can only be rendered slow by means that make the skin cold and inelastic, or by 1 Physiologie Médicale de la Circulation du Sang. Paris, 1863. Pp. 68 and 121, and elsewhere. VOL. V. 2 positions that make the application of the apparatus more difficult. In all cases the spring carrying the pad should be screwed down so as to give its greatest pressure. In the account of the traces thus obtained, the rapid beats will be first described; after these the slow ones, by which means an idea can be best formed of the relation between curves at first sight so different as those produced when the heart's action is over 100 and those when it is below 50 in a minute (compare Figs. I. and VI.). There is a great similarity in traces from pulses above 105 to those over 140 in a minute; and the description of one will include them all. Figure 1. is from a heart beating 125, and it represents all the characteristic features. The movements of the lever are very extensive and sudden, so as to give the impression that they depend more on its momentum than on the heart's action; but that such is not the case is shewn by applying the instrument a little way from the point of greatest pulsation, when (as in Fig. II.) all the same elements appear, though much less ample and otherwise modified. The main ascent commences abruptly immediately after a slight rise and fall (a, Figs. I. II.), and is always broken about midway (b) by a small fall; it is followed by a most considerable and rapid descent, which carries the lever in an unbroken line, down to a point almost as low as that from which it started. Subsequently to this comes a less sudden rise (ƒ), which reaches about as high as the break in the main ascent; its summit is not nearly so sharp as the previous one, and from it a fall, frequently a little irregular, commences slowly, becoming more rapid, though it is interrupted by a slight rise (9), after which it continues to sink until it reaches the lowest point of the trace, from which it makes a sudden slight ascent (k), which soon becomes more gradual, continuing until the rise (a) from which the description commenced. Neglecting for the present small differences in the relative durations of these components, the pulse of 140 differs from that of 110 a minute in the movements being more extensive and consequently the angles more sharp, the intermediate rate is being intermediate in character. In the pulse of about 90 a minute (Fig. III.) another small rise and fall appears (e) in addition to those previously described, which is very constant, and becomes more considerable when the heart's action is slower. Here also, as shewn in Fig. IV. in a trace taken directly after Fig. III. between the sixth and seventh ribs, there is sometimes seen a reduplication of the first part of the main rise (b, c, Fig. IV.), which is disguised in Fig. III. probably by the momentum of the lever. Another point in which it differs from the quicker pulses is in the formation of a second undulation (b) in the main descent before it reaches its lowest point. The main ascent also is not so extensive. When about 70 beats are made in a minute the main rise can frequently be shewn to be doubly broken (b, c, Fig. v.); but these often get merged into one curved line. The subsequent fall (d) is here seen to have become much diminished, and the next rise and fall (e) of greater duration. In the slow pulses (Figs. VI. IX.) the fall after the small rise preceding the main ascent (a) is inconsiderable, or nil, which makes that rise appear as part of the main one, which is not the case. The rise c has now become more marked, while d has diminished so much that it is no longer the highest point of the trace, that now being at the end of the rise preceding the main descent (ƒ), which is frequently found to be double. It is to be noticed that as the pulse gets slower, the generally ascending line between k and a gets longer; also that at all rates there is a great similarity in shape in the fall and rise between the points h and k, which is quite characteristic of that part of the curve. A precise knowledge of the causes of these various changes in the direction of the human apex trace will always be somewhat deficient, from the impossibility of vivisectional verification, and from the fact that the relations of the organs concerned is different in man to what it is in animals, from which, otherwise, arguments from homology might have been more extensively employed. By means of synchronous traces from the exterior and interior of the heart of the horse Marey explains his apex trace, |