ON ZOOLOGY. 127 



imbibed by their lungs. While she has bestowed 

 on others, a more simple apparatus, and blood of 

 a lower temperature ; as exemplified in the am- 

 phibia and common fishes, in which, from living 

 principally in the water, where the element is 

 cooler, and the air in diminished proportions, 

 a single heart and a reduced caloric or heat has 

 been sufficient : and more especially in the insect 

 and worm tribes, where (as explained before) a 

 still much less complicated mechanism has an- 

 swered all the respiratory purposes required by 

 those animals. In this arrangement, like every 

 other in which nature has been concerned, we 

 again see a wonderful adaptation of the means 

 to the end ; and that while the utmost precaution 

 has been used to preserve the vital principle, no 

 more capability of excitement has been given, 

 than was necessary to answer the purposes 

 required. 



We come now to the organs of sense and vo- 

 luntary motion, by which animals are principally 

 distinguished from vegetables, and which, by 

 the attributes they have conferred upon our own 

 species, have elevated man very far indeed above 

 every other part of the creation. Upon this inte- 

 resting subject, my time will not allow me to do 

 more than offer a few general observations ; re- 

 serving a particular account of each organ of 

 sense for a future lecture. 



Sensation has philosophically been stated to 



