The following observations continue some of those reported previously to the Society by Mr. N. B. Dreyer and myself (1) and by Dr. K. Sassa and myself (2). But in the present instance the technique has been considerably modified in the hope of securing finer discrimination between the contraction forms obtained. The speed and intensity of the reactions of mammalian muscle with its blood supply intact rendered desirable greater lightness in the moving parts of the myograph. The free vibration rate of the isometric myograph now used has been more than 900 a second; its damping such that when suddenly released from a torsional deviation, approximately that obtaining in the muscle observations, the vibrations ceased to be visible under tenfold enlargement in about 0·03 sec. The registration of the myograph movement has been by optical projection on a travelling photographic plate, time being recorded on the plate by a rotary shadow-marker of the pattern devised by Mr. Bull, of the Institut Marey, Paris. The reflex preparation has been
tibialis anticus
muscle in the spinal cat, decerebrated and free from drugs. The stimulus used has been a single break-shock given by an automatic key and applied by platinum electrodes 5 mm. apart to the central stump of the cut and isolated afferent nerve (popliteal, internal saphenous or digital branch of musculocutaneous) or, for the motor control, to the peripheral stump of the cut motor nerve (peroneal), kathode proximally for the former, kathode distally for the latter. The magnification of the muscle movement has been sixty times: that is, for a myogram of 30 mm. height recording a tension of 915 grm., the muscle,
e. g
., of 12 cm. length, shortened 1/240 of its length; the myograms are thus practically isometric.
VIBRATION RATE OF THE TAIL OF A RATTLESNAKE