4 . INTRODUCTION 



The science of Physiology was first concerned with the activities 

 of adult bodies. These activities are dependent upon structure 

 to the same extent that the activities of a machine, such as a steam- 

 engine or an automobile, are related to the structural relationships 

 of its parts. Physiology and Morphology must, therefore, be 

 studied together as the problem of function and structure, if one 

 desires an adequate knowledge of living bodies. The animal is 

 "something happening" rather than an actionless piece of 

 machinery. One may infer how its parts "work" by an exam- 

 ination of their structure, just as the operation of an engine might 

 be inferred from an examination of its mechanism; but complete 

 knowledge can be obtained only when an understanding of the 

 engine's " morphology " is correlated with observations and 

 experiments upon its " physiology," or manner of action. Since 

 Anatomy, Embryology, Histology, and Cytology have their mor- 

 phological as well as their physiological aspects, the sciences of 

 Morphology and Physiology are everywhere related as the struc- 

 tural and functional aspects of Uving organisms. To understand 

 fully the problem of form without considering that of function is a 

 manifest impossibility. 



Origin of the Individual. ■ — Although it might be included under 

 the head of Morphology and Physiology, the study of Embryology, 

 or the process of development by which individual animals come 

 into existence, must be ranked as one of the major problems of 

 biological science. Embryology is a phase of Anatomy, since it 

 deals with the origin of structure. In studying it from this aspect, 

 one examines embryos in their successive stages and likewise their 

 histological and cytological organization. However, the more 

 important aspect of the origin of the individual is not the descrip- 

 tion of successive stages, but rather an account of what " happens " 

 in development. Now that the successive stages have become 

 well known in so many animals. Embryology is becoming more of a 

 physiological than a morphological science. There is the same 

 relationship between structure and activities as in the problem of 

 form and function. Psychology and Pathology might likewise 

 be included here. The origin of the individual is, in fact, only the 

 problem of form and function as it appears in other than adult 

 phases. 



Organism and Environment. — The relation of the animal to its 

 surroundings, or environment, presents many complex problems. 



