LIFE AND WRITINGS OF ROBERT WHYTT, M.D. 113 



terially bettered the understanding of the principles of activity therein operative. 

 The same forms of expression are still applicable to the principle recognised by 

 Whytt, and to that acknowledged in the systems of the present day ; namely, 

 the continual application of such and such a stimulus succeeded by the appointed 

 effect of each stimulus according to its nature, and the circumstances attending 

 its operation. 



Numerous authors are cited from Aristotle to Boyle, Glisson, Redi, Wood- 

 ward, and Kaau Boerhaave, who have vaguely spoken of motions in animals 

 after decapitation, as if they had anticipated Whytt in his peculiar views. 



Of these, Glisson, Harvey's contemporary, who, as the author of the idea of 

 irritability independently of the nerves, holds a high rank among physiologists, 

 ascribes the movements in decapitated animals to what he terms perception of 

 impressions without sensation. It is possible that the idea in Glisson's mind 

 justly represented the modern reflex action ; but his mode of expression is too 

 vague to have had much influence on the progress of this part of physiology. 

 Whytt recounts the experiments of Redi and Kaau, such as removing the 

 brain and cutting off the heads of tortoises, without destroying life even for many 

 months ; and suddenly cutting ofl* the head of a cock in rapid motion, after 

 which he continued to run for several yards. Such experiments led Whytt to 

 make the following observation, which brings his ideas still more close to the 

 modern notion of the reflex action of the spinal cord, — " the spinal marrow does 

 not seem altogether derived from the brain and cerebellum, but probably pre- 

 pares a fluid itself, whence it is enabled to keep up the vital and other motions 

 for several months in a tortoise after the head is cut off." 



To discover the extent of Whytt's influence on the subsequent progress of the 

 physiology of the nervous system, some notice must be taken of the labours of a 

 few of his immediate and more recent successors, particularly Unzer, Prochaska, 

 and Marshall Hall. 



Unzer or Untzer of Halle, though younger than Whytt, began to publish 

 before him. But his " Principles of Physiology," the only work in which he 

 touches closely on Whytt's subject, was not published till some years after the 

 death of the latter. For an excellent translation of this book, published in 1851, 

 English physiologists are indebted to Dr Laycock. Unzer was well acquainted 

 with Whytt's writings. Speaking of what he terms nerve-forces, he says, — 

 " Modern physiologists, whose names Europe knows and honours, Haller, Zim- 

 merman, Whytt, and Oeder, have rendered much service to this department of 

 physiology, by contributing materials thereto." 



It has been imagined that Unzer's views are far in advance of Whytt's 

 This idea rests on a misunderstanding of what Unzer taught. Unzer's book is 

 indeed full of ability, and is even at this day of surpassing interest to the physi- 

 ologist, but it abounds in language peculiar to the author to so great an extent. 



