THE SCOPE OF BIOLOGY 3 



the histories of the Earth, animals, and plants, or so-called obser- 

 vational sciences, as the residue for natural history. 



It remained, however, for Lamarck in particular, during the 

 opening years of the nineteenth century, to attain a vision of the 

 unity of animal and plant life and to express it in the term biology. 

 But biology is something more than a union of plant science — 

 botany — and animal science — zoology — under one name ; for 

 it endeavors, in addition to describing the characteristics of plants 

 and animals, to unfold the general principles underlying both. 

 Accordingly animal biology, the subject of the present volume, 

 is the study of the basic principles of life with especial reference 

 to animals, including Man. 



B. Biological Sciences 



Thus the biologist has as his field the study of living things — 

 what they are, what they do, and how they do it. He asks, how 

 this animal or that plant is constructed and how it works — and 

 this he attempts to answer. He would like to ask, and often does 

 ask, why it is so constructed and why it works the way it does, 

 but then he passes beyond the scope of science into the realm of 

 philosophy. 



These queries of the biologist reflect the two primary viewpoints 

 from which biological phenomena may be approached: the mor- 

 phological in which interest centers upon the form and structure of 

 living things; and the physiological in which attention is concen- 

 trated upon the functions performed — the mechanical and chem- 

 ical engineering of living machines. Clearly, however, it is im- 

 possible to draw a hard and fast .distinction between morphology 

 and physiology because in the final analysis structure must be 

 interpreted in terms of function, and vice versa. But again, the 

 fields of morphology and physiology naturally resolve themselves 

 into special departments of study, depending on the level of analy- 

 sis of structure or of function which is emphasized. Thus mor- 

 phology stresses the general form of the animal or plant; anatomy, 

 the gross structure of individual parts, or organs; histology, the 

 microscopic structure of organs, or tissues; cytology, the com- 

 ponent elements of tissues, or cells, and the physical basis of life, 

 or protoplasm. Similarly, physiology investigates the activities 

 of animals and plants, the functions of organs, the properties of 

 tissues, the phases of cell life, and finally the physico-chemical 



