bivouac can they come to realize how far-flung indeed are 

 the battle-lines of the armies of science how rich and 

 diversified is the territory from which knowledge has 

 driven ignorance and superstition. And they must realize 

 also how impossible it is for them to conduct their opera- 

 tions at all times in entire independence. The results of 

 physics and chemistry are indispensable weapons for the 

 biologist; geology takes the field with paleontology for 

 the study of fossil forms ; while on the other hand the ad- 

 vance posts of zoology provide the students of many a 

 human science with a secure base of operations. 



I need not speak of the inter-relations of the several 

 biological sciences, for these have been sufficiently ex- 

 plained in the earlier discourses. I shall pass directly to a 

 description of the elements of the present science of 

 zoology and of its history, so far as this is necessary for a 

 clear understanding of the various divisions of the subject 

 and of their connections; and finally I shall endeavor to 

 show how through its human materials zoology articulates 

 directly with other fields of knowledge. 



ZOOLOGY is the science that deals with the structure, de- 

 velopment and inter-relationships of animals, with the 

 workings of their parts, their activities and their relations 

 to their environment, and with the factors that determine 

 their forms. We may recognize two great divisions of the 

 subject, which are concerned respectively with static and 

 with dynamic principles, though the materials of both 

 divisions are the same namely, all animals throughout the 

 entire range from the highest to the lowest. It is of course 

 clear that morphology the science of structure cannot 

 be absolutely separated from physiology the science of 

 function in its widest sense for we do not know of organic 

 structures that play absolutely no part in an animal's 



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