AN ELEMENTARY SYSTEM OF PHYSIOLOGY. BY JOHN BOSTOCK, M. D. P. G. S. F. R. S. L. S. AND H. S. M. R. I. MEM. AND LATE V. PRES. OF THE MEDICAL AND CHIRURGICAL, AND MEM. OF VOL. II. LONDON: PRINTED FOR BALDWIN, CRADOCK, AND JOY. 1826. ΤΟ ARTHUR AIKIN, ESQ. F.L.S. & G.S., SECRETARY TO THE SOCIETY OF ARTS, &c. MY DEAR SIR, THE first volume of this Treatise I had proposed to have inscribed to our much valued friend, Dr Marcet, under whose inspection the work was commenced, and from whom I received many important suggestions, respecting both the plan and the mode of execution. His premature death prevented me from fulfilling my design. To the present volume I beg leave to prefix your name. A friendship, which may be said to have been transmitted to us from our parents, which commenced in our childhood, and which has continued to the present period, without the slightest interruption, might alone be sufficient to justify my choice. But, independently of any private feelings of this description, I am anxious to embrace this opportunity of giving my public testimony to your excellent moral qualities, and to your varied scientific acquirements; qualities which are the more esteemed the more they are known; and, acquirements which have been uniformly employed in the improvement of the useful arts, or in the advancement of knowledge. Believe me, my dear Sir, Your very sincere and faithful Friend, J. BOSTOCK. Upper Bedford-Place, March 5th, 1826. PREFACE. THE reception which the first volume of this treatise experienced, could leave no doubt in my mind as to the necessity of completing the work; and I lament that certain circumstances, which were unavoidable, have delayed for so long a period the publication of the second part. As, however, the circumstances to which I allude no longer exist, I may indulge a hope that the third volume will succeed the present at a considerably shorter interval. I have, as nearly as possible, pursued the same method of giving an account of the best established facts, and the most approved hypotheses; freely offering my remarks upon them, and pointing out any part which appeared to be objectionable. I have, however, found it a very difficult task to arrive at any satisfactory conclusion, with respect to many of the topics that are discussed in this volume. For, singular as it may appear, although most of them profess to be established on the basis of direct experiments, and such as would appear not to be of not to be of very difficult execution, yet we shall find that every step of the track through which I have had to pass, is on debateable ground. On this account, I have frequently felt it necessary to dissent from the opinions of the most eminent physiologists of the age; but when I have done this, |