OCTOBEU 22, 1896] 



NA TURE 



601 



yriipiiig about in a dim lii;lu, holly iliscussing whetht-r the brain 

 and spinal curd could affecl the beat of the heart. To all these 

 discussions Weber's experiment came as a great light in a dark 

 place. 



There is no need for me to insist hosv this knowledge that 

 impulses descending the vagus slow or restrain the heart beat, 

 and the knowledge genetically dependent on this, that impulses 

 reaching the heart along the cardiac sympathetic nerves from 

 the thoracic spinal cord, stir up the heart to more vigorous or 

 frequent beats, have since served as a guide for the physician in 

 the intricate problems of cardiac disease, and that with in- 

 creasing security as our knowledge of the details of the actions 

 has increased. The knowledge may not always have been 

 wisely used. On this point perhaps I niaj' be allowed to repeat 

 <he caution which I may have given elsewhere, concerning the 

 dangers of taking a new physiological fact direct and straight, 

 raw and bleeding as it were, from the laboratory to the bedside. 

 The wise physiologist takes care, even in physiology itself, not 

 10 use a new fact as an explanation of old problems without a 

 due testing and a direct verification of its applicability. How 

 much more is it needful that the doctor who sails not on the 

 calm seas of the phenomena of health, but amid the troubled 

 tempests which we call disease, should not hastily and heedlessly 

 rush to make practical use of a new fact, tempting as the use 

 may be. until he also has tested its applicability by that clinical 

 study which is his only sure guide. But this is by the way. 



In the second place, as a mere method, Weber's discovery has 

 in physiological experinientatiim borne most important fruit. 

 Before Weber's experiment many an investigation, not only on 

 the vascular system itself, hut in many other branches of physio- 

 logy, came to a standstill or went astray because the experi- 

 menter had not the means on the one hand to stop or slacken, or 

 on the other to quicken and sliru|) the heart, without interfering 

 largely with the object of his research. Thanks to W'eber's 

 experiment and what has come out of it, that can now be done 

 with ea.se, and thus solutions have been obtained of problems 

 which otherwise seemed insoluble. 



In the third place, the experiment has had a profound 

 and widespread influence by serving to introduce a new 

 idea, iliat idea which we now denote by the word inhibition. 

 Before the experiment, though men's minds were gradually 

 getting clearer concerning the nature of a nervous impulse, all 

 known instances of the action of a nervous impulse had for the 

 result an expenditure of energy ; and it was a still open, though 

 hotly debated question whether in such actions as when a muscle 

 was thrown into contraction by a nervous impulse this feature of 

 expenditure was not impressed on the muscle by the very nature 

 of the impulse itself. That ipieslion the experiment answered 

 in the negative once and for all. Whatever the exact nature of 

 a nervous impulse, it was evidently of such a kind that it might 

 on occasion check expenditure and bank up energy in an in- 

 creased potential store. Observation soon showed that the heart 

 and vagus was no solitary example. It was recognised that the 

 due regulation of many of, if not all, the so-called nervous 

 centres was secured not merely by the intrinsic forces of passive 

 rest making themselves felt in the absence of stimulation, but 

 also, and even more so, by the alternating play of antagonistic 

 influencus. Throughout all the .sciences the resolving a stability 

 seemingly due to intrinsic causes into an equilibrium arising out 

 of the balance of o|)posing forces, has again and again marked 

 a step forward ; and it is perhaps not too much to say that a like 

 analysis, prompted by the story of the vagus and the heart, has 

 profoundly modified all our conce|>lions of Ihe way in which 

 nervous impulses, sweeping along the intricate yet ordered net- 

 work of paths in the brain and spinal cord, determine the conduct 

 of life. The idea has of course been abused as well as used, as 

 what idea has not ? Such a word as inhibition could not but 

 fail to have a blessed .sound in the ears of the ignorant ; the idea 

 has been ignoranlly and wrongly applied ; but this is of little 

 moment in view of the help which it has given to wise and well- 

 directed inquiry. 



.\nd the idea has spread with fruitful results beyond the limits 

 of nerv.ius impulses ; it has been carried deep down into the 

 very innermost molecular processes of life. The closer we pene- 

 trate into the physical-chemical events through which living 

 mailer grows, lives and dies, the clearer does it seem that life 

 itselt is a shifting outcome of two opposing sets of changes — one 

 synthetic constructive, the other destructive, analytic, and that 

 the key lo this and that riddle of vital action lies within the 

 grasp of him who can clearly lay hold of the mutual relations of 



NO. 1408, VOL. 54] 



these conflicting changes. The .story of the vagus and the 

 heart is a tale, not of the heart alone, not of the nervous .system 

 alone, but of all living matter. The light which first shone in 

 the experiment of the brothers Weber may in a sense be said to 

 have gone out into all the lands of physiology. 



Let me now turn your attention lo an experiment made a few 

 years later. This is also an experiment made on a living animal, 

 and whatever good may have come out of that to which it has 

 given rise must be reckoned as the fruit of an experiment. 



In 1851, Claude Bernard made known that division of the 

 cervical sympathetic led to a widening of the blood-vessels and 

 a warming of the ear and other parts of the head and neck. 

 This was the beginning of what may rightly be called the great 

 vaso-molor knowledge. It may be true that more than a 

 hundred years before, in 1727, Du Petit had observed much the 

 same thing, but nothing came out of it ; the germinal time had 

 not yet arrived. It may be true that other observers since Du 

 Petit had divided the cervical sympathetic, and noted theefiects; 

 but these had their attention directed chiefly to changes in the 

 ]iupil. It may be true that Brown-Sequard and Waller, a few 

 months before Bernard himself was able to do so, supplied the 

 complement to the original experiment by showing that stimula- 

 tion of the peripheral part of the divided sympathetic con- 

 stricted the blood-vessels and reduced the temperature. All 

 this may be true, but there remains the fact that with Bernard's 

 experiment the new light began ; that experiment marks the 

 beginning of our va.so-motor knowledge. 



I have already spoken of the prolonged discussions, which just 

 before the date of Huxley's studentship were taking place, 

 touching the question whether or no the blood-vessels were 

 muscular and contractile. That question had, meanwhile, been 

 definitely settled by Henle's demonstration, in 1840, that the 

 tissue in the middle coats of arteries really consisted in part of 

 mu.scular tissue, of the kind known henceforwards as plain 

 muscular tissue. But for some years no use was made of this 

 discovery in the direction of explaining the intervention of the 

 nervous system in the government of the circulation. That 

 began with Bernard's experiment. 



It would, I venture to think, be sheer waste of your time and 

 mine, if I were to attempt to labour the theme of the large 

 share in our total physiological knowledge which is now taken 

 up by the vaso-motor system and all that belongs to it, and of 

 the extent to which the physiology of that system has woven 

 itself into pathological doctrines, and helped medical practice. 

 I would simply ask the lecturer on physiology in what stress he 

 would find himself if he were forbidden in his teaching to say a 

 word which would imply that the calibre of the blood-vessels 

 was influenced by the contraction of their walls through nervous 

 influence ; or ask the student how often, in an examination of to- 

 day, he would have to sit seeking inspiration by biting his pen, 

 or staring at the roof, if he too, in his answers, could never refer 

 to vaso-motor actions. Whatever part of physiology we touch, 

 be it the work done by a muscle, be it the various kinds of 

 secretive labour, be it that maintenance of bodily temperature 

 which is a condition of bodily activity, be it the keeping of the 

 brain's well-being in the midst of the hydrostatic vicissitudes to 

 which daily life subjects it — in all these, as in many others, we 

 find vaso-motor factors intervening ; and, to say nothing of the 

 .share taken by these in the great general pathological conditions 

 of inflammation and fever, they also have to be taken account of 

 by the doctor in studying the disordered physiological processes 

 which constitute disease, wh.atever be the tissue aff'ected by the 

 morbid conditions. Take away from the physiological and 

 pathological doctrines of to-day all that is meant by the word 

 vasomotor, and those doctrines would be left for the most part 

 a muddled unintelligible mass. To so great an extent as that 

 which Bernard's experiment began entered into our modern 

 views. 



It was Bernard's good fortune, but deserved good fortune, to 

 announce, almost at the same time, two fundamental discoveries. 

 For I venture to claim for his discovery of the formation of 

 glycogen in the liver, briefly indicated in 1850, more fully ex- 

 pounded in 1851, an importance only second, if second, to that 

 of the cxpeiiment with which we have just been dealing. 



To judge of its importance we must look at it from more than 

 .)ne point of view. 



At the time when Huxley was sitting at the feet of Wharton 

 Jones, the teaching of the Schools was largely governed by the 

 view that the animal organism, in contradistinction to the vege- 

 table organism, was essentially destructive in its chemical actions. 



