34 INTRODUCTION. 



the most enllglitened curiosity, for expanding in no 

 common degree, our conceptions of tlie harmony 

 and beauty of the works of nature, and for raising 

 to the highest pitch our admiration of the inex- 

 haustible wisdom of the great Creator. 



The very position which the Cetacea occupy in 

 the animal kingdom, forms in itself a subject of the 

 deepest wonder and astonishment. 



Our readers are probably aware that of the four 

 divisions into which Cuvier, the great master of 

 natural science, has divided the animal kingdom, 

 the first consists of the vertebratae. The verte- 

 bratae, which include the animals of the most perfect 

 structure, are again subdivided into four great 

 classes, forming a natural descending series beauti- 

 fully simple and complete ; being 1st, Mammalia or 

 Quadrupeds,— 2dly, Birds, — 3dly, Reptiles, — and 

 4thly, Fishes. Each of these classes is characterized 

 by a diversity of locomotive powers, which depends 

 on the quantity of inspiration, inasmuch as this is 

 the grand source whence the muscular system de- 

 rives its irritability and strength. The efficiency of 

 respiration again, depends upon the relative amount 

 of blood which is forced into the respiratory organs 

 in a given space of time, and the relative amount of 

 oxygen which operates upon the circulating fluid. 

 Now, the respiratory organs in the first class of the 

 vertebratae, viz. the Mammalia, are of the most 

 perfect kind, and perform their functions under 

 very favourable circumstances, — the circulating 

 fluid, at each inspiration, being brought into im- 



