xxviii On Comparative Anatomyf and the 



ter, and others, on the digestion of food in the human sto- 

 mach, and in many other animals, ahout which process vari- 

 ous erroneous theories had been previously entertained. The 

 consideration of this process, as conducted in animals, with 

 an examination of the admirable organs for the purpose, will 

 form a very interesting part of our course.^^ 



6. " Comparative anatomy becomes necessary in ascertain- 

 ing the action of organs. All the functions have ceased long 

 before the human body can be opened, and it is only in the 

 inferior animals that we can presume to make experiments 

 examining the movements of the different organs before the 

 principle of life has escaped." It is chiefly in this field of in- 

 quiry, that we have obtained the correct knowledge which 

 we now possess, of many of the animal functions.^^ Nor can 

 the supposition be admitted, that this study savours of cru- 

 elty : every humane mind is shocked at the idea of wantonly 

 giving pain to any animal ; but when such pain is requisite 

 to illustrate the animal physiology, the sacrifice is indispen- 

 sable and justifiable. Without it, we might, in all probabi- 

 lity, have been ignorant at this day of the sublime discovery 

 of the circulation of the blood, and deprived of the impor- 

 tant benefits resulting from it to mankind. 



7. By comparing the internal organization of different 

 animals, we are enabled to distinguish those parts which are 

 common in the structure of every animal body, and essen- 

 tially necessary for the performance of the vital functions | 

 from such as are peculiar to certain animals, and exclusive- 

 ly subservient to their necessities, economy, or enjoyment. 

 I'hus when we find particular organs impei'fectly developed 

 ill certain animals, or extracted^^" in some, and naturally want- 

 ing in a third, without any essential injury to life, we arc 

 then enabled to judge of the rank which these organs hold 

 even in the human species : and by the circumstance of life 

 being supported, and the functions of llic body going on, 

 after a cessation in the performance of certain functions, 

 ♦AC are not only taught the propriety of attempting the sav- 



