RECENT ADVANCES IN SCIENCE. 351 



into even distant parts of knowledge. The good of the experiment by 

 itself is soon merged in the general good of scientific inquiry. The 

 science of physiology, and by implication the art of medicine, is built 

 up in part on experiments on living animals; in part only, but that 

 part is so woven into all the rest that any attempt to draw it out would 

 lead to a collapse of the whole. 



It is because each experiment or observation is thus a thread caught 

 up in a close-set web, that its value depends not alone on the mere 

 result of the experiment or observation itself, but also, and even more 

 so, on the time at which, and on the circumstances and relations under 

 which it is made. This truth the real worker in science has borne in 

 upon him again and again; it is this which leads him to that humility 

 which has ever been the outward token of the fruitful laborer. He 

 feels that it is not so much himself working for science as science 

 working through him. 



Let me attempt to illustrate this by dwelling on some two or three 

 single observations in physiology, made almost at the time or very 

 soon after the time at which Huxley was a student. It will, I think, 

 be seen that each of them has reached a long way in its bearing on the 

 science of physiology and on the art of medicine; that the full effect of 

 each has been dependent both on what went before and on what has 

 happened since, and though they were all made, so to speak, long ago 

 some of their fruits were brought in as it were yesterday, and their full 

 fruition is perhaps not yet accomplished. 



I will first invite your attention to a single experiment, for, though 

 repeated on various animals, we may call it a single experiment, which 

 in the fall of the year 1845 Ernest Heinrich Weber, then professor of 

 anatomy at Leipzig, and his brother Eduard Eriedrich, reported to au 

 assembly of Italian scientific men in Naples, and of which they subse- 

 quently published an account in Mullet's Archiv in 1846. Makin'g use 

 of the recently introduced rotating electro magnetic apparatus (the 

 physical discovery begetting the physiological one), they found that 

 powerful stimulation of the vagus nerves had the unexpected result of 

 stopping the heart from beating. 



This single experiment, which I may quote by the way as a typical 

 experiment on a living animal — for it is impossible to imagine how the 

 discovery of this action of the vagus on the heart could have been 

 made otherwise than by an experiment on a living animal — this single 

 experiment has made itself felt far and wide throughout almost the 

 whole of idiysiology. 



In the first place, it has made us understand in a way impossible 

 before the experiment how, through the intervention of the nervous 

 system, the work of the heart is tempered to meet the strain of varying 

 circumstances. As I said a little while back, only a few years before 

 even eminent observers were groping about in a dim light, hotly dis- 

 cussing whether the brain and spinal cord could affect the beat of the 



