HANDBOOK OF PHYSIOLOGY 



CHAPTER I 



INTRODUCTORY 



BIOLOGY is the science that treats of living things, and it is divided 

 into two main branches, which are called respectively Morphology 

 and Physiology. Morphology is the part of the science that deals 

 with the form or structure of living things, and with the problems 

 of their origin and distribution. Physiology, on the other hand, 

 treats of their functions, that is, the manner in which their individual 

 parts carry out the processes of life. To take an instance : the eye 

 and the liver are two familiar examples of what are called organs ; 

 the anatomist studies the structure of these organs, their shape, their 

 size, the tissues of which they are composed, their position in the 

 body, and the variations in their structure met with in different 

 parts of the animal kingdom. The physiologist studies their uses, 

 and seeks to explain how the eye fulfils the function of vision, and 

 how the liver forms bile, and ministers to the needs of the body in 

 other ways. 



Each of these two great branches of biological science can be 

 further subdivided according as to whether it deals with the animal 

 or the vegetable kingdom; thus we get vegetable physiology and 

 animal physiology. Human Physiology is a large and important 

 branch of animal physiology, and to the student of medicine is 

 obviously the portion of the science that should interest him most. 

 In order to understand morbid or pathological processes it is neces- 

 sary that the normal or physiological functions should be learnt first. 

 Physiology is not a study which can be put aside and forgotten when 

 a certain examination has been passed; it has a most direct and 

 intimate bearing in its application to the scientific and successful 

 investigation of disease. It will be my endeavour throughout the 

 subsequent pages of this book to point out from time to time the 

 practical relationships between physiology and pathology. 



