OF FORM AND STRUCTURE. 167 



tion of a species. These considerations, again, may 

 be classed under three divisions, viz. external organ- 

 isation, internal anatomy, and chemical composition. 

 The first of these belongs more especially to the 

 zoologist, the second to the anatomist, and the third 

 to the chemist: all are fit objects of enquiry; but as 

 all are not equally essential to our present purpose, 

 we shall confine our observations chiefly to the first. 

 (109.) For the sake of simplification, the word 

 form or structure may commonly be used as syno- 

 nymous with external organisation. If a person, 

 unacquainted with natural history, was put into an 

 immense store-room, filled with all sorts of plants, 

 animals, and minerals confusedly mixed together, 

 and then desired to sort and separate them, he 

 would, even were he a clown, begin to place the 

 plants in one heap, the animals in another, and the 

 minerals in a third. If, after this was done, he 

 was again directed to make a more particular assort- 

 ment of the animals only, he would assuredly sepa- 

 rate the quadrupeds from the birds ; and these, again, 

 from the fishes and the serpents. No one will deny 

 that this would be the natural process : and we may 

 therefore infer, that external form is the chief and 

 primary mode by which nature herself teaches us to 

 know her productions : and that we need only de- 

 scend to an examination of internal structure, when 

 this resource fails, and we are obliged to enter upon 

 minute and delicate investigations. But as many have 

 laid an undue stress upon the importance of internal 

 over external organisation, and thereby, as we con- 

 ceive, embarrassed the path of the student with un- 

 necessary difficulties, it may be as well to explain, 

 M 4 



