376 



COMPARATIVK PHYSIOLOGY. 



examined into by a species of experiment on one's self that is 

 as simple as it is valuable. 



Comparative.— It is hoped that the various figures accompa- 

 nied by descriptions, introduced in this and other chapters, will 



■Stg. 



Fig. 301. 



Fio. 303. 



Fio. 301.— A. Pulmonary sac. B. Respiratory leaflets of Scorpio occitaniuTlklteT 



Blanchard). 

 Fie. 308.— Left pulmonary sac, viewed from dorsal aspect, of a spider (after OugSs). 



Pm, pulmonary lamellae; Sig^ stigma, or opening to former. 



make the relations of the circulation and respiration in the va- 

 rious classes of animals, whether terrestrial or aquatic, evident 



Fie. 303. —A. B. Tadpoles with external branchiae (after Huxley), re, nasai sacs; a, 

 eye; o, ear; k. 6, branchise; m, mouth; z, homy jaws; s, suckers; d, opercular 

 (or gill) fold. C. More advanced froe^s larva, y, rudiment of hind-limb; k. 8, 

 single branchial aperture. Owing to figure not having been reversed, this aper- 

 ture seems to lie on right instead of left side. 



without extended treatment of the subject in the text. What 

 we are desirous of impressing is that throughout the entire 

 animal kingdom respiration is essentially the same process ; that 



