friO 



POPULAR SCIENTIFIC LECTURES. 



by authority, or is only chosen because it 

 agrees with that which it is wished to believe 

 true, any crack may then hopulesxly destroy 

 tho whole fabric of conviction. The con- 

 vinced disciples must therefore claim for each 

 individual part of such a fabric the same de- 

 gree of infallibility ; for the anatomy of Hip- 

 pocrates just as much as for fever crises ; 

 every opponent must only appear then as 

 stupid or depraved, and the dispute will thus, 

 according to old precedent, bo so much the 

 more passionate and personal, the more un- 

 certain is the basis which is defended. We 

 have frequent opportunities of confirming 

 these general rules in the schools of dogmatic 

 deductive medicine. They turned their in- 

 tolerance partly against each other, and partly 

 against the eclectics who found various ex- 

 planations for various forms of disease. This 

 method, which in its essence is completely 

 justified, had, in the eyes of systematists, the 

 defect of being illogical. And yet the great- 

 est physicians and observers, Hippocrates at 

 the head, Arfitceus, Galen, Sydenham, and 

 lioerhaave, had becomo eclectics, or at any 

 r:Ue very lax systematists. 



About tho time when we seniors com- 

 menced the study of medicine, it was still 

 t;nuer tho influence of the important dis- 

 coveries which Albrecht von jgnJUer had made 

 on tlie excitability of nerves ; "and which ha 

 had placed in connection with tho vitalistic 

 theory of the nature of life. Haller had ob- 

 served tho excitability in the nerves and 

 muscles of amputated members. The roost 

 surprising tiling to him was, that the most 

 varied external actions, mechanical, chemical, 

 thermal, to which electrical ones were subse- 

 quently added, had always the same result 

 namely, that they produced muscular con- 

 traction. They were only quantitatively 

 distinguished as regards their action on the 

 organism, that is, only by the strength of the 

 otritation ; he designate:! thorn by the com- 

 mon name of stimulus ; he called the altered 

 condition of the nerve the excitation, and its 

 capacity of responding to a stimulus the ex- 

 citability, which was lost at death. This en- 

 tire condition of things, which physically 

 speaking asserts no more than that the 

 nerves, as concerns the changes which take 

 place in them after excitation, are in an ex- 

 ceedingly unstable state of equilibrium ; this 

 was looked upon as the fundamental property 

 of animal life, and was unhesitatingly trans- 

 ferred to the other organs and tissues of the 

 body, for which there was no similar justifi- 

 cation. It was believed that none of them 

 were active of themselves, but must receive 

 an impulse by a stimulus from without ; air 

 and nourishment were considered to be the 

 normal stimuli. The kind of activity seemed, 

 on the contrary, to be conditioned by tha 

 specific energy of tho organ, under the influ- 

 ence of the vital force. Increase or diminu- 

 tion of the excitability was the category un- 

 der which the whole of tho acute diseases 

 were referred, and from which indications 

 were taken as to whether tho treatment 

 should be lowering or stimulating. The rigid 



one-sidetlness and the unrelenting logic witi 

 which Robert Brown had once worked out 

 this system was broken, but it always fur- 

 nished the leading points of view. 



Tho vital force had formerly lodged 03 

 ethereal spirit, as a Pnouma in tho arteries ; 

 it had then with Paracelsus acquired the 

 form of an Archens, a kind of useful Kobold, 

 or indwelling alchemist, and had acquired 

 its clearest scientific position as " soul of 

 life," anima inscia, in Georg Ernst Stahl, who, 

 in the first half of the last centuryT^ffBs pro- 

 fessor of chemistry and pathology in Halle. 

 Stahl had a clear and acute mind, which is 

 informing and stimulating, from the way in 

 which he states the proper question, even in 

 those cases in which he decides against our 

 present views. Ho it is who established tho 

 first comprehensive system of chemistry, 

 that of phlogiston. If wo translate bin 

 phlogiston into latent heat, the theoretical 

 bases of his system passed essentially into 

 the system of Lavoisier ; Stahl did not then 

 know oxygen, which occasioned some false 

 hypotheses ; for instance, on the negative 

 gravity of phlogiston. Stahl's " soul of liio" 

 is, on the whole;, constructed on the pattern 

 on which the pietistic communities of that 

 period represented to themselves the sinful 

 human soul ; it is subject to errors and pas- 

 sions, to sloth, fear, impatience, sorrow, in- 

 discretion, despair. The physician rrmst 

 first appease it, or then incite it, or punish 

 it, and compel it to repent. And the way in 

 which, at the same time, he established tho 

 necessity of the physical and vital actions 

 was well thought out. The soul of life gov- 

 erns the body, and only acts by means of tho 

 physico-chemical forces of the substances 

 assimilated. But it has tho power to bind 

 arid to loose these forces, to allow them full 

 play or to restrain them. After death the re- 

 strained forces become free, and evoke putre- 

 faction and decomposition. For the refuta- 

 tion of this hypothesis of binding and loos- 

 ing, it was necessary to discover the law of 

 the conservation of force. 



The second half of tho previous century 

 was too much possessed by tho principles of 

 rationalism to recognize openly Stahl's " soul 

 of life." It was presented more scientifically 

 as vital force, Vis vitalis, while in the main it 

 retained its functions, and under the name 

 of" nature's healing power" it played a prom- 

 inent part in the treatment of diseases. 



The doctrine of vital force entered into tho 

 pathological system of changes in irritability. 

 The attempt was made to separate the direct 

 actions of the virus which produce disease, 

 in HO far as they depended on tho play of 

 blind natural forces, tho symptomnta mvrbi, 

 from those which brought on the reaction of 

 vital force, the symptomala readioni.i. The 

 latter were principally seen in inflammation 

 nnd in fever. It was the function of the phy- 

 sician to observe tho strength of thif. reaction, 

 and to stimulate or moderate it according to 

 circumstances. 



The treatment of fever seemod at that time 

 to be the chief point ; to be that part of 



