642 



POPULAR SCIENTIFIC LECTUPtES. 



lologlst. In &ic theoretical vtewg ho I'.ivored 

 the vitalistic hypothesis, but in the most 

 essential points he was ft natxiral philoso- 

 phor, firm and immovable ; for him, nil theo- 

 ries were but hypotheses, which luvd to be 

 tested by facts, and about which facts could 

 alone decide. Even the views upon thosa 

 points which most easily crystallize into dog- 

 mas, on the mode of activity of the vital 

 force and the activity of the conscious soul, 

 he tried continually to define more precisely, 

 to prove or to refute by means of facts. 



And, although the art of anatomical inves- 

 tigation was most familiar to him, and he 

 therefore recurred most willingly to this, yet 

 he worked himself into the chemical and 

 physical methods which were more foreign to 

 him. Ho furnished the proof that fibxiue is 

 dissolved in blood ; he experimented on tho x 

 propagation of sound in such mechanisms as 

 are found in the drum of the ear ; he treated 

 the action of the eye as an optician. His 

 most important performance for the physi- 

 ology of the nervous system, as well as for 

 the theory of cognition, was the actual definite 

 establishment of the doctrine of the specific 

 energies of the nerves. In reference to the 

 separation of the nerves of motor and sensi- 

 ble energy, he showed how to make the ex- 

 perimental proof of Bell's law of the roots of 

 the spinal cord so as to be free from errors ; 

 and in regard to the sensible energies he not 

 only established the general law, but carried 

 out a great number of separate investigations, 

 to eliminate objections, and to refute false 

 indications and evasions. That which 

 hitherto had been imagined from the data of 

 overy-day experience, and which had been 

 sought to be expressed in a vague manner, in 

 which the true was mixed up with the false ; 

 or which had just been established for indi- 

 vidual branches, such as by Dr. Young for 

 the theory of colors, or by Sir Charles Bell 

 for ftie motor nerves, that emerged from 

 Mailer's hands in a state of classical perfec- 

 tion a scientific achievement whose value I 

 am inclined to consider as equal to that of the 

 discovery of the law of gravitation. 



His scientific tendency, and more especially 

 his example, were continued in his pupils. 

 We had been preceded by Schwann, Henle, 

 Ileichert, Peters, llemak ; I met as fellow- 

 students E. Du Bois-Beymond, Virchow, 

 Briicke, Ludwig, Traube, J. Meyer, Lieber- 

 kiihn, Hallmann ; we were succeeded by A. 

 von Gracfe, W. Busch, Max Bchultze, A. 

 Schneider. 



Microscopic and pathological anatomy, the 

 study of organic types, physiology, experi- 

 mental pathology and therapeutics, ophthal- 

 mology, developed themselves in Germany 

 tinder the influence of this powerful impulse 

 ar beyond the standard of rival adjacent 

 countries. This was helped by the labors of 

 those of similar tendencies among Miiller's 

 contemporaries, among whom the three 

 brothers Weber of Leipzig must first of all be 

 mentioned, who have built solid foundations 

 in the mechanism of the circulation, of tne 

 muscles, of the joints, and of the ear. 



The attack was made wherever a way cor 

 bo perceived of understanding one of tho 

 vital processes ; it was assumed that they 

 could bo understood, and success justilkil 

 this assumption. A delicate and copious 

 technical apparatus has been developed in the 

 methods of microscopy, of physiological 

 chemistry, and of vivisection ; the latter 

 greatly facilitated more particularly by tho 

 use of ansesthetic ether and of the paralyzing 

 curara, by which a number of deep problems 

 became open to attack, which to our genera- 

 tion seemed hopeless. The thermometer, tho 

 ophthalmoscope, the auricular speculum, the 

 laryngoscope, nervous irritation on the liv- 

 ing body, opened out to tho physician possi- 

 bilities of delicate and yet certain diagnosis 

 where there seemed to be absolute darkness. 

 The continually increasing number of proved 

 parasitical organisms substitute tangible 

 objects for mystical entities, and teach liin 

 surgeon to forestall the fearfully subtle dis- 

 eases of decomposition. 



But do not think, gentlemen, that the 

 struggle is at an end. As long as there are 

 people of such astounding conceit ns to 

 imagine that they can effect, by a few clevt-r 

 strokes, that which man can otherwise only 

 hope to achieve by toilsome labor, hypothe- 

 ses will bo started which, propounded as dog- 

 mas, at once promise to solve all riddles. 

 And as long as there are people who believe 

 implicitly in that which they -\\ish to be true, 

 so long will the hypotheses of the former 

 find credence. Both classes will certainly 

 not die out, and to the latter the majority 

 will always belong. 



There are two characteristics more particu- 

 larly which metaphysical systems have 

 always possessed. ]n the first place man is 

 always desirous cf feeling himself to be a 

 being of a higher order, far beyond the stand- 

 ard of the rest of nature ; this wish is satis- 

 fied by the spiiitualiste. On the other hand, 

 he would like to believe that by his thought 

 he was unrestrained lord of the world, and 

 of course by his thinking with those concep- 

 tions, to the development of which he has 

 attained ; this is attempted to be satisfied by 

 the materialists. 



But one who, like the physician, has 

 actively to face natural forces which bring 

 about weal or woe, is also under tho obliga- 

 tion of seeking for a knowledge of the truth, 

 and of the truth only ; without considering 

 whether, what ho finds, is pleasant in one 

 way or the other. His aim is one which is 

 firmly settled ; for him the success of fac1 

 is alone finally decisive. He must endesiM-r 

 to ascertain beforehand, what will bo tin- 

 result of his attack if he pursues this or thin 

 course. In order to acquire this foreknowl- 

 edge of what is coming, but of what has not 

 been settled by observations, no other 

 " method is possible than that of endeavoring 

 to arrive at the laws of facts by observations ; 

 and we can only learn them by induction, by 

 the careful selection, collation, and observa- 

 tion of those cases which fall Tinder the law. 

 When we fancy that we have arrived at a 



