114 DR seller's memoir OF THE 



that before the light which recent discoveries have thrown on the subject it must 

 have been difficult to decipher. Whence it is probable that the influence of 

 Unzer's writings over the progress of nerve-knowledge has often been overrated. 

 What may be described as his general view of " vital and other involuntary 

 motions," does not differ essentially from Whytt's, — that is, he regards them as 

 originating in an external impression, conveyed by nerves to the brain and mind, 

 whence a motor influence is transmitted by nerves to the organ to be called into 

 motion. In one respect, under this head, he goes beyond Whytt, namely, in the 

 full manner in which he treats of instincts, " which," he says, " nature has so 

 placed under the control of external impressions, and so arranged the natural 

 functions of the organs, that animals cannot prevent their manifestation." But 

 in what has been mistaken for a nearer approach to the modern " reflex action" 

 in Unzer's views, there is really a retrograde movement. The word " reflex" is 

 employed by him in a sense altogether different from its acceptation at present. 

 When he says that sensory impressions are reflected into motor force, what he 

 means is, that reflexion takes place through communications between nervous 

 filaments, altogether independently of the l)rain or spinal cord. And while he 

 speaks of ganglia being sometimes concerned in this reflexion, he does not regard 

 those as subordinate nervous centres, but merely as mechanical obstacles, along 

 with others which he names, by which the ascent of an impression to the brain 

 is impeded.* Whence it follows that this kind of reflex action is merely a revival 

 of the old view of Willis as to sympathetic acts being the effect of communica- 

 tions between nerves in their course, — an idea rejected by Whytt, and disproved 

 by Monro. 



Prochaska, who appears next after Unzer to have taken up the views initi- 

 ated by Whytt, belongs to the last quarter of the eighteenth, and the first twenty 

 years of the nineteenth century. He was Professor of Anatomy and Diseases of 

 the Eye, first at Prague for twelve years, and then at Vienna. His Latin work, 

 " De Functionibus Systematis Nervosi," was first published in 1784. He shows 

 himself familiar with the views of Whytt, whose works he repeatedly quotes. 

 He is also well acquainted with Unzer's works. It is undeniable that Prochaska 

 made a considerable advance on the views of Whytt. And yet a few quotations 

 will prove how little these two physiologists differ in principle. " Thus," Proch- 

 aska says, " although a nerve be necessary to sensation and motion, it does 

 not excite motion or feel alone, but feels by means of the brain, which, when an 

 impression made on a nerve is brought to it, communicates the impression to the 

 mind ; and the nerve produces motion by means of a muscle, when the nerve 

 descends to the muscle and excites it to movement."! Such a statement might 



* Unzer, " Principles of Physiology," translated by T. Laycock, M.D., pp. 223, 224. 

 f Prochaska, " Dissertation on the Functions of the Nervous System," translated by T. Lay- 

 cock, M.D., pp. 407, 408. 



