520 PHYSIOLOGY CHAP. 



On the twenty-first day both motor zones of the cerebral 

 cortex were exposed and stimulated by electrical currents. On 

 exciting the left sigmoid yyrus single contractions were evoked, 

 as well as epileptic fits confined to the right side. On exciting 

 the right sigmoid gyrus weak currents only elicited contractions 

 of the left ear and left facial muscles. Very strong currents 

 evoked weak contractions of the left limbs, but never epileptic 

 attacks. 



From these facts observed after unilateral trausection of the 

 entire mid-brain of the cat it is clear that there is never total 

 paralysis of sensation and motion in the opposite half of the 

 animal. After three weeks it regains its capacity of walking and 

 jumping ; the forced postures and movements seen directly after 

 the operative act improve progressively, and the sensory disorders 

 improve rapidly. 



Apart from the special cases we have been considering, it may 

 be stated in general terms that the intensity of the symptoms of 

 unilateral section of the mid-brain, including the cerebral peduncle, 

 depend on whether the transection is complete or not. One effect 

 of the coutralateral motor paresis is the circus movement of the 

 animal, which is generally to the opposite side, sometimes also to 

 the side of the lesion ; in the first case, which is the rule, the 

 curvature of the spinal axis predominates in the second, the 

 greater extension of the limbs of the operated side, in comparison 

 with the paretic limb of the opposite side, prevails. 



In the monkey, and more particularly in man, the effects are 

 greater. Clinical cases, no less than experiments on animals, 

 enable us to form an idea of the importance of the cerebral 

 peduncle, inasmuch as it contains the sensory and motor cerebro- 

 spinal conducting paths. In correspondence with the localisation 

 and extent of lesions of the peduncle there is crossed motor, 

 sensory, or mixed paralysis, partial or complete. 



X. The physiology of the optic thalami leaves much to be 

 desired. This is due in great measure to the difficulty of attacking 

 these masses of grey matter without damaging the surrounding 

 organs. The method proposed and carried out by Lo Monaco in 

 our laboratory undoubtedly indicates considerable progress from 

 the point of view of technique. It consists in the partial transec- 

 tion of the corpus callosum, which produces no apparent disturb- 

 ance, and separation of the two hemispheres so as to expose the 

 thalami, in order to excite them or remove them entirely or in part. 



Contrary to the vie\vs of other authors, electrical or other 

 stimulation of the thalami causes neither painful sensation nor 

 motor reaction, provided the stimulation does not spread to the 

 cerebral peduncles nor the anterior quadrigeminal bodies (Ferrier, 

 Lo Monaco). The effects of the destruction or removal of the 

 thalami varies according to different experimenters, and according 



