96 LAY SERMONS, ADDRESSES, AND REVIEWS. 



discrimination, classification, and distribution of animalss 

 he is termed a zoologist. 



For the purposes of the present discourse, however, I 

 shall recognise none of these titles save the last, which I 

 shall employ as the equivalent of botanist, and I shall 

 use the term zoology as denoting the whole doctrine 

 of animal life, in contradistinction to botany, which 

 signifies the whole doctrine of vegetable life. 



Employed in this sense, zoology, like botany, is di- 

 visible into three great but subordinate sciences, mor- 

 phology, physiology, and distribution, each of which 

 may, to a very great extent, be studied independently 

 of the other. 



Zoological morphology is the doctrine of animal form 

 or structure. Anatomy is one of its branches ; develop- 

 ment is another ; while classification is the expression 

 of the relations which different animals bear to one 

 another, in respect of their anatomy and their develop- 

 ment. 



Zoological distribution is the study of animals in 

 relation to the terrestrial conditions which obtain now, 

 or have obtained at any previous epoch of the earth's 

 history. 



Zoological physiology, lastly, is the doctrine of the 

 functions or actions of animals. It regards animal bodies 

 as machines impelled by certain forces, and performing 

 an amount of work which can be expressed in terms of 

 the ordinary forces of nature. The final object of phy- 

 siology is to deduce the facts of morphology, on the one 

 hand, and those of distribution on the other, from the 

 laws of the molecular forces of matter. 



Such is the scope of zoology. But if I were to content 

 myself with the enunciation of these dry definitions, I 

 should ill exemplify that method of teaching this branch 

 of physical science, which it is my chief business to- 



