THE HISTORICAL DEVELOPMENT OF NEUROPHYSIOLOGY 33 



^r<u>.3 ■ 



FIG. ii. Lejt: Alexander Stuart's experiment contirming the observations of Stephen Hales that a 

 decapitated frog convulses on being pithed and then becomes immobile. (From Stuart, A. Crooman 

 Lectures 1738. London: Woodward, 1739.) Ri^ht: Robert Whytt whose experiments demonstrated 

 reflex action in decapitated animals and the eflTects of spinal shock. (From the portrait in the Royal 

 College of Physicians, Edinburgh, by courtesy of Mr. G. R. Pendrill.) 



and confirmed this experiment and described it in a 

 lecture to the Royal Society in 1738. 



Whytt in his experiments on the frog came very 

 close to defining the segmental reflex. He also noted 

 spinal shock, for he remarked that a decapitated frog 

 could not be made to move immediately after transec- 

 tion although if one waited about 15 min. it would 

 react to stimuli. But perhaps the most striking of his 

 observations is the one in which he anticipated 

 Sherrington in regard to the stretch reflex. "Whatever 

 stretches the fibres of any muscle so far as to extend 

 them beyond their u.sual length, excites them into 

 contraction about in the same manner as if they had 

 been irritated by any sharp instrument, or acrid 

 liquor" (183, p. 9). 



With the publication of Whytt's work physiologists 

 were divided between regarding the movements of 

 spinal animals as a lingering in the cord of powers 

 originally derived from the brain, and the view that 

 the spinal marrow itself was capable of sensation and 

 movement. Whytt inclined to the latter view in his 

 explanation of the writhings of decapitated and 

 eviscerated snakes. "We are naturally led to con- 

 clude," he said, "that they are still in some sense alive, 

 and endued with feeling, i.e. animated by a sentient 

 principle." 



Before the end of the century, Whytt's publications 

 had been followed by thase of Unzer (185), of Halle 



185. Unzer, Johann August (i 727-1809). Ersle Griinde einer 

 Physiologie der eigenltchten thierischen Nairn thicrischer hovper 



and of his pupil Proehaska (186) who was a practising 

 ophthalmologist in Prague. Both these men contrib- 

 uted more in systematization and formulation at the 

 conceptual level than in the addition of new experi- 

 mental facts. In England, the Sydenham Society gave 

 Ijoth their books to the same translator, Thomas 

 Laycock (the teacher of Hughlings Jackson), and 

 through him the word reflexion became the accepted 

 term. Unzer postulated several sites where reflexion 

 of impressions might take place — in the brain, in the 

 ganglia, in bifurcations of nerves and in plexuses. Only 

 if they reached the brain would these impressions be 

 consciously perceived. Unzer in discussing automatic 

 movements protected himself against the attacks en- 

 countered by soine of his predecessors by saying that 

 "the animal machines are mysteriously and inscru- 

 tably endowed by the Creator." 



Proehaska, with one foot in the past, believed in a 

 sensorium commune where automatic reflexion took 

 place and thought this might be in the medulla or the 

 cord but did not agree with Unzer that reflexion 

 might be at the level of the ganglia. He reverted to 



Leipzig: Wiedmanns, 1771; English translation by T. 

 Laycock. Principles of a Physiology of the Mature of Animal 

 Organisms. London: Sydenham Society, 1851. 

 186. Prochaska, JiRi (1749-1820). Part III: De functionibus 

 systematis nervosi, et observationes anatomico-pathologi- 

 cae. In: Adnotationum Academicarum . Prague: Gerle, 1784; 

 English translation by T. Laycock. Dissertation on the 

 Functions of the Nervous System. London: Sydenham Society, 

 1851. 



