Vlll PREFACE 



pathology. It is supplementary to such volumes. It does not start like 

 the modern test in functional pathology, with a consideration of the 

 diseased condition, and then proceed to analyze the possible causes and 

 consequences of the disturbances of function which this exhibits; but 

 it deals with the present-day knowledge of human physiology in so far 

 as this can be used in a general way to advance the understanding of 

 disease. In a sense it is therefore an advanced text in physiology for 

 those about to enter upon their clinical instruction, and at the same 

 time, a review for those of a maturer clinical experience who may desire 

 to seek the physiological interpretation of diseased conditions. 



In attempting to fulfil these requirements, it has been deemed essen- 

 tial to go back to the fundamentals of the subject, and to explain as 

 simply as possible the physical and physicochemical principles upon 

 which so large a part of physiological knowledge depends. Physiology 

 may be considered as an application of the known laws and facts of 

 physics and chemistry to explain the functions of living matter, and it is 

 only after the extent to which this application can be made has been 

 appreciated, that the knowledge may be used to serve as the foundation 

 upon which a superstructure of clinical knowledge can be built. 



In order that the volume might be maintained of reasonable size, it 

 has been necessary to select certain parts of the subject for particular 

 emphasis, the basis of selection being the degree to which our knowledge 

 clearly shows the value of the application of physiological methods both 

 of observation and of thought in the study of diseased conditions. This 

 has not been done to the extent of omitting the apparently less essential 

 parts, for these have been treated in sufficient detail to link the others 

 together so as to preserve a logical continuity, and show the bearing of 

 one field of knowledge on another. There are however certain parts 

 of the science, particularly the physiology of nerve and muscle, of the 

 special senses, and of reproduction, for which application in the general 

 fields of medicine and surgery is limited, and these parts have been 

 omitted entirely. It has been judged that this perhaps somewhat arbi- 

 trary selection is justified on the ground that the ordinary text in 

 physiology covers these subjects sufficiently, except for the specialist, 

 for whom on the other hand, no adequate review would have been pos- 

 sible within the limits of such a volume as this. With reference to bio- 

 chemistry, no attempt is made to review the properties or describe the 

 characteristic tests of the various chemical ingredients of the body tis- 

 sues and fluids. This is already sufficiently done in the textbooks on 

 biochemistry, and in the numerous manuals on clinical methods. Bio- 

 chemical knowledge is treated rather from the physiologist's stand- 

 point, as an integral part of his subject, particular attention, neverthe- 



