108 



On the Myogram of the Flexor-reflex evoked by a Single 



Break-shock. 

 By K. Sassa and C. S. Sherrington, Pres. E.S. 



(Received December 20, 1920.) 



(From the Physiology Laboratory, Oxford.) 



Our object has been to compare the reflex contraction of a muscle when 

 evoked by a single induction shock with the contraction evoked from the 

 same muscle when a similar stimulus is applied directly to the muscle's motor 

 nerve. The experiments extend some observations previously reported in 

 these Proceedings (2) and in the'Journ. of Physiology ' (6). The literature 

 of the subject was given in those papers and for it reference may be had to 

 them. 



Method. 



The reflex preparation employed has been the spinal cat, the muscle being 

 tibialis anticus. Either before or after the spinal cord had been transected 

 the animal was decerebrated. The spinal transection and the decerebration 

 were performed under deep anaesthesia. The spinal transection was in some 

 cases made three to ten days prior to the decerebration. The seat of spinal 

 transection was usually at the posterior end of the thoracic region, but some- 

 times at the anterior end of the cervical region. All the hind-limb muscles 

 except tibialis anticus were immobilised by nerve section, or in the case of 

 extensores, digitorum and peronei, tenotomy. The limb was fixed by steel 

 drills in tibia and femur, the drills being clamped to unyielding uprights on 

 the experimental table. The tendon of tibialis anticus was attached by a 

 short length of waxed fishing line to an isometric myograph of the torsion- 

 wire pattern. The vibration period of this recorder was somewhat less than 

 0"01". The afferent nerves of the limb were severed and those used for 

 stimulation were popliteal in the ham, musculo-cutaneous on the dorsum of 

 the foot, and internal saphenous, femoraUs, and external cutaneous below the 

 groin. 



The break induced current used as stimulus was obtained by the automatic 

 opening of a contact in the primary circuit. The striker opening the contact 

 was attached to a spindle carrying the recording surface, the moment of 

 delivery of the stimulus being thus registrable on that surface. The spindle was 

 horizontal and rested on bearings similar to those of an Atwood machine ; it 

 was operated by the fall of a weight. After the reflexes and their latencies 



