worked on the other. At 19, he graduated and commenced his travels. He was the student of Douglas, in London, in whom he inspired such confidence that he made Haller promise to help him in his investigations into the development of bone. The same restless, knowledge seeking spirit carried him next to Paris, where his enthusiasm is said to have been kindled to such a pitch under the teachings of le Dran and Winslow, that he stole a body from the grave for material upon which to work. He had to leave Paris to escape punishment and next we find him in Basel, at the age of twenty, teaching anatomy to the students. In 1736, he was now 28, he was elected professor of anatomy and surgery at the newly established university of Göttingen. Proud of so early a recognition of his talents, he labored for the success of this institution until students streamed in to the young college from all parts of Europe. He was now teaching anatomy, surgery and botany. A regular chair of physiology had not yet been established. Besides these labors, he kept up his work in natural history, wrote a great number of literary papers and occupied what leisure was still left in composing poetry. At the age of 45 he was so completely broken down that he had to retire from all active duties. We form some idea of his "iron industry, his almost incredible memory, his profound culture in all the branches of human knowledge" by the story which has come down to us that no one of his Göttingen colleagues ever ventured to visit him without a formal preparation upon the theme to be made the subject of conversation. He is said to have written 12,000 reviews! And yet he never left a letter unanswered. According to all testimony, there was never in medicine a laborer so untiring. Rudolphi näively remarks in the preface to his own work on physiology: "If you should ask all the authors of works on physiology, which book they considered the best, it could not be thought strange if each

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21

one would reply, his own. But if you should go further and ask each one what book he considered next best, I am convinced that every one without exception would name Haller's. And surely," Rudolphi continues, "what seems to all the second best must be in reality the first."

Besides this, his greatest work, Haller was the author of three distinct bibliographies, of anatomy, surgery and practical medicine, which have been characterised as "monuments of his incredible literary activity, which stand isolated in medical literature, and will remain for all time as inexhaustible sources of information to the medical historian." Colin, in his Comparative Physiology, called Haller "L'homme des faits, l'homme de l'observation et des experiences; son œuvre est le point de depart de toute la physiologie moderne. Cruveilhier spoke of it as "full of discoveries." His original investigations were so numerous and so valuable, as to justly entitle him to the place assigned him by posterity as the "Founder of Modern Physiology." The latter part of his life he spent at Berne in the exercise of the highest civic powers in the state, though even here he found leisure to prosecute his favorite scientific and literary pursuits. The sculpture on the pillar of fame in history has chiseled his name beside that of Aristotle and Goethe and Humboldt.

Characteristics of Physiologists.

And what then were the characteristics of these two great physiologists? They were cautious men. Harvey proved his study twenty years before he preached it. Haller made 109 experiments before he published his discovery of the independent irritability of muscle. They were truthful men. The bitter opposition of their contemporaries, the experimentation of all posterity, have never shaken the facts they advanced. They were simple men; in all their tastes. and habits; among other things it is recorded of both, they

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CHARACTERISTICS OF PHYSIOLOGISTS.

were men of gentle deportment. Above all, they were working men. And if the question were asked as to the influence of the study of physiology on the character of the physician, there could be no more fitting answer than a reference to the lives of men who have drifted into it as a life study because of their natural adaptability to it.

One point more. Physiology offers to the physician a present refuge in time of trial. The vicissitudes of practice, the rancor of rivals, the unceasing combat against prejudice and ignorance and superstition make life a burden at times even where envy marks it a great success. It is in dark hours like these, and who but knows them, that the physician may turn to the study of physiology. No man of the world, no man of other profession than natural science, may ever know or be able to understand the peace, in the way of fresh inspiration for future work, which nature offers at the foot of her altars. The chief reward of every kind of mental work-higher than either wealth or fame—is its effect upon the character. The study of medicine is peculiarly excellent in developing the mental faculties. Having elements in it belonging to both literature and science— the bride and her spouse in modern education-it most happily blends the virtues and balances the faults, pertaining to a purely literary or a purely scientific pursuit.

I should fall short of the high purpose of our convocation, to-night, should I fail to impress upon you clearly the trial which science demands at your hands before she will adorn you with the stamp of her nobility. It is the trial of work, the chief characteristic, as you have seen, in the lives of our eminent men; work with the sacrifice of self; work which is only stimulated to higher efforts by the achievements of others; work with something, at least, of that feeling in the breast of Themistocles-a poor illegitimate boy-Ruler of Athens he became-who was alone

THE CONSERVATION OF FORCE.

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sorrowful and distressed amidst the general rejoicing over the great victory at Marathon. And when they asked him why his eyes were red with weeping and why he walked the streets with disheveled hair, he made them that reply which foretold his future success: "It was the trophies of Miltiades that would not let him sleep."

LECTURE II.

THE CONSERVATION OF FORCE.

CONTENTS.

The Alphabet of Science-Indestructibility of Matter-No Matter with. out Force-Solar Origin of Heat of Coal-Correlation of ForcesMachinery, a Means of Changing Force-Clocks, Water-Wheels, Winds, Windmills and Steam Engines-The Equivalence of the Forces-The Conservatory of Arts and Trades-Motion from HeatMotion from Electricity-The Electric Light-The Sun as the Source of Power-Source of Solar Force-The Nebular Hypothesis-The Channel of Mt. Pilatus-The Perpetuity of Force-Physiological Force-Excretions, the Products of Combustion-Animal Bodies as Machines-The Force Value of Foods-Physiological, Correlative with Physical Force.

Within the past quarter of a century has been generally promulgated one of those fundamental principles or laws in natural science which, like that of gravitation or of terrestrial revolution, marks a most memorable epoch in its history. What especially distinguishes this law and lifts it to a plane above all other laws of nature, is the fact that it spans, in its giant grasp, every order of existence. It reduces to shape and order the primitive chaos of the universe, governs the movements of the heavenly bodies thus created, generates the various forms of the mighty forces about us, and, while engaged in this stupendous work, con

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INDESTRUCTIBILITY OF MATTER.

cerns itself no less with the insignificant phenomena of life upon our insignificant globe; swinging systems of planets in their spheres, upon the one hand, and, on the other, springing flowers from the bosom of the earth. I need hardly say that this law, which has been announced as the primal law of all science, and which has been characterised by Faraday as the highest law in physical science that our faculties permit us to perceive, is the law of the Conservation and Correlation of Force. That is, it is the law which has demonstrated that force, as well as matter, is indestructible, however much its form may change, and which has proven that all the forces, light, heat, electricity, motion, etc., may be converted, the one into the other, quantity for quantity, in exact equivalents, no force being ever created anew and no force being ever lost.

We shall study this law to-night more especially in its bearing upon human life, and shall try to make it plain that what is known as life, or vital force, is only part of the general store of force in the universe, borrowed for the time being from other physical forces and being continually surrendered again in the various phenomena of life, as in heat, motion, secretion, reproduction, intellection, etc.

Indestructibility of Matter.

It is now more than a century ago that it was known among men of science that matter is indestructible. When we speak of the destruction of matter, we refer simply to the form of the matter. For instance, we say matter is destroyed by fire. But when we come to analyse the products of combustion, we find in the smoke, the gases and the ash precisely the same elements as before. We proceed to weigh these various products in delicate scales to discover only pounds and ounces and grains, just the same as before. Fire has only changed the form. So when we