In jeder Zelle des tierischen Organismus findet ein ununterbrochener Stoffverbrauch statt. Zur Erhaltung seiner Lebensfahigkeit bedarf der Organismus der Erganzung dieser EinbuBen. Der tierische Organismus ersetzt seine verausgabten Bestandteile durch Verwertung vegetabilischer oder animalischer Organismen. Infolgedessen bestehen die "Nahrungs stoffe," die er in sich aufnimmt, mit Ausnahme von Wasser und anorga. nischen Salzen, aus auBerordentlich komplizierten chemischen Verbin dungen: EiweiBkorpern, Kohlehydraten und Fetten pflanzlicher und tierischer Herkunft. Bevor jedoch der Nahrungsstoff in die den ganzen Organismus um fassende Blutbahn eintritt und zusammen mit dem Blut den einzelnen Zellen des Organismus zugefiihrt wird, muB er eine ganze Reihe phy sischer und chemischer Veranderungen durchmachen. Die Notwendig keit dieser Veranderungen ergibt sich hauptsachlich aus folgenden Er wagungen: 1. Die Nahrungsstoffe bestehen in der Mehrzahl der FaIle aus un loslichen, in hohem Grade komplizierten chemischen Verbindungen. Sie miissen in eine losliche Form iibergefiihrt und in resorbierbare Verbin dungen umgewandelt werden. 2. Die Zellen des tierischen Organismus haben die Fahigkeit, ihre Verausgabungen nur durch Aufnahme streng bestimmter chemischer Verbindungen zu erganzen. Indessen befinden sich jedoch in den Nah rungsstoffen gewohnlich dem Organismus fremde chemische Verbin dun gen. Zwecks Einverleibung dIU' Nahrungsstoffe in das Blut und ihrer Ver arbeitung zu einem fUr die Zellen adaquaten Nahrmaterial existiert im tierischen Organismus ein spezielles System - das System des Ver dauungskanals."

Pavlov A BIOGRAPHY By B. P. BABKIN THE UNIVERSITY OF CHICAGO PRESS I. P. PAVLOV Foreword THE following pages, which contain an account of the life and scientific achievements of the great Russian physiologist, Ivan Petrovich Pavlov, must be considered only as material for a future, more comprehensive biography. The interval since Pavlovs death has not been sufficiently long for the collection of all the necessary data on his life and work, even by biographers living in Russia. For me, a resident of Canada, it has been much more difficult to obtain the information I desired. Then, inevitably, the biographer is handicapped by a certain lack of perspective in writing of a great man recently departed. He is, as it were, still among us. We see and hear him as he was at our last meeting we regard him from a per sonal angle, which makes it difficult to maintain strict objectivity in the description of his character and work. Nevertheless, I de cided to write a biography of Pavlov for the following reasons. I am Pavlovs senior surviving pupil. I knew him well for thirty five years from 1901 to the time of his death in 1936. I served for ten years as his assistant in the Department of Physiology at the Institute of Experimental Medicine in St. Petersburg. Our associ ation in the laboratory developed into a lasting friendship. These circumstances entitle me to speak of Pavlov as a contemporary who was familiar with his scientific activity throughout the greater part of his life. Since the year 1949 is the centenary of I. P. Pavlovs birth, I felt that for me it was a duty as well as a privilege to com municate to those interested in his life and work all that I know about him. There was anotherconsideration which influenced me in my decision to write this biography. It seemed to me that an account of Pavlovs life by one of his contemporaries who was closely associated with him might be of some value to future students of the cultural development of Russia. Pavlov belonged to the younger generation of those remarkable men who made possible the astounding cultural development of vii FOREWORD nineteenth-century Russia. Less than one generation separated Pa vlov from such men asPirogov anatomist and surgeon, Mendeleev and Butlerov chemists, Sechenov physiologist, Botkin phy sician, Soloviev historian, Chicherin political economist, Tur genev, Tolstoy, and Dostoevski novelists, Tchaikovsky, Mus sorgsky, and Rimski-Korsakov composers, and many others. Pavlov and his contemporaries continued this brilliant tradition. The mental development of Pavlov and his attitude toward life in general were formed during the sixties and seventies of the past century. Profound political and social changes were taking place in Russia during the reign of Alexander II 1855-81. The youth of the period was full of idealism and of a sincere desire to serve its country and humanity. Pavlov retained these high ideals all through his life, steadfastly believing in truth, justice, and liberalism and the all-important role of science. In 1917 this astounding cul tural development of Russia was suddenly disrupted, and new political and social ideas were forcibly imposed on the country. This book consists of four parts. Part I comprises the biography proper and my reminiscences of Pavlov. Parts II, III, and IV deal with his scientific achievements in the physiology of the cardio vascular, digestive, andcentral nervous systems. As far as possible, the scientific material has been presented in a form comprehensible to any intelligent lay reader. I hope, however, that specialists in these fields will also find there certain things which may interest them. I have been sparing in the use of quotations from the scien tific literature, referring the reader whenever possible to mono graphs rather than to individual articles. In the preparation of the manuscript I have had the help of a number of persons, to whom I should like here to express my sin cere thanks...