120 PHILOSOPHY OF ZOOLOGY. 



CHAP. II. 



INTRNAL CHARACTERS. 



The examination of the internal characters of animals has 

 hitherto been chiefly carried on by those who have practised 

 the art of dissecting, as connected with medical studies. 

 Among many naturalists, the examination of the structure 

 of animals is considered unnecessary, with a view to their 

 classification, however useful it may be to the physiologist. 

 There has resulted from this neglect a superficial method of 

 examining, describing, and arranging animals, observable in 

 many works on zoology ; great importance being attached to 

 characters drawn from organs remotely connected with those 

 most essential in the functions of life. Sounder views, how- 

 ever, are now entertained by the most distinguished sup- 

 porters of the science The internal structui-c of animals is 

 now investigated, in order to explain then- functions ; and 

 the methods of classification which arc employed, owe their 

 stability to the justness of the views entertained of their pecu- 

 har organisation. The employmentof the external characters 

 requires little labour or reflection, and the accuracy of the 

 results is at all times doubtful. The use of the internal 

 characters presupposes considerable exertion and patience, 

 but the results are to be depended upon. Manual dex- 

 terity is indeed requisite, but it can be acquired by prac- 

 tice. 



In order to examine the internal structure of an animal 

 with any degree of success, some attention is required to its 

 condition at death. In many molluscous animals, the or- 



