ESSAY III. THE MECHANICS AND PHYSICS OF THE BODY 31 ESSAY IV. THE NERVOUS SYSTEM 58 ESSAY V. THE BODY 94 CONCLUSION 107 INDEX 113 INTRODUCTION The unscientific public is extremely prone, and not altogether without reason, to take medicine as a starting-point, and arrange all biological science around it. As it is, moreover, apt to gauge the interest and utility of every branch of this science from a practical point of view, and bestows most attention upon that which it imagines is of the greatest service to the doctor, I think a series of popular essays on physiology could not commence with more advantage, at any rate to physiology, than by briefly discussing, not with what it deals, for that is pretty generally known, but what is its relation to medicine. Further, as the doctor is more easily discussed than medicine, the physiologist will be more manageable for our immediate purpose than physiology in the abstract, so we will devote the first few pages to the question of how his labours benefit the patient. Everyone knows the doctor, and everyone knows that physiology deals with the ‘functions of different organs of the body’; but the public rarely meet the physiologist, except in the fanciful caricatures of his enemies, which though frequently personal are rarely accurate. These rancorous libels, if anyone heeded them, would tend to raise doubts as to whether the physiologist was a good companion for the doctor, and if it were not as well for them to see as little of each other as possible.