the physiology of the nervous system—compared with which all the rest of physiology, judged either from a practical or from a theoretical point of view, is a mere appendage—has been gained by experiment, that its fundamental truths have come to us through inquiries entailing more or less vivisection. By meditating over the differences in structure visible in the nervous systems of different animals, a shrewd observer might guess at the use of some particular part; but till verified by experiment, the guess would remain a guess; and experiment shows that such guesses may be entirely wrong. Where experiment has given a clew, careful observations have frequently thrown light on physiological problems. Without the experimental clew, the phenomena would ever have remained a hopeless puzzle, or have served to bolster up some baseless fancy. What disease, or what structure in what animal, could ever have made us acquainted with that "inhibitory" function of the pneumogastric nerve which the vivisectional experiment of Weber first detected? What a light that one experiment has thrown on the working of the nervous system! What disease could have told us that which we have learned from the experiments of Du Bois-Reymond and of Pflüger? Where would physiological science be now if the labors of Flourens, Brown-Séquard, Schiff, Vulpian, Goltz, Waller, and others, were suddenly wiped away from the records of the past? Yet each of these names recalls long series of experiments, some of them painful in character, on living animals.
I repeat, take away from the physiology of the nervous system the backbone of experimental knowledge, and it would fall into a shapeless, huddled mass.
The chemistry of living beings, one would imagine at first thoughts, might be investigated without distressing the organisms which formed the subjects of research. The labors of Lavoisier and Priestley, who first made clear the chemistry of respiration, if they entailed no use of the knife, caused at times a no less painful suffocation; while the great advances which have been made in this branch of the study during the last quarter of a century, and are still being made, necessitate almost daily vivisection, in order that the gases of the blood may be studied in exactly the same condition as they are in the living body. Even still more bloody has been the path by following which we have gained the knowledge we now possess of the chemistry of digestion and nutrition. I have only to mention the names of Bidder, and Schmidt, and Bernard, to call to the mind of the physiological student important results, nearly all reached through vivisection. The shifts and changes of the elements within our body are too subtile and complex to be divined from the results of the chemical laboratory; the physiologist has to search for them within the body, and to mark the compounds changing in the very spot where they change; otherwise all is guess-work.