CONTENTS. xvii 



SECTION III. 



Kidneys and their Function. 



Place and Form, 425. Excretory duct, 426. Pelvis of kidney, sec- 

 tion, minute structure, 427. Function, composition of urine, 429. 

 Comparison of kidneys and lungs, 430. Diagrams illustrating circula- 

 tion of C and O, and of circulation of elements of organic matter, 432. 

 Comparative Morphology of Kidneys : Mammals, birds, reptiles, 433. 

 Insects, Crustacea, mollusca, 434. 



SECTION IV. 

 The Skin and its Function. 



Function, 435. Exhalation, excretion, structure of skin, 436. Su- 

 dorific glands, 437. Lungs, kidneys, and skin compared, 438. 



Comparative Morphology and Physiology of Skin. — General remarks, 

 438. Mammals, birds, reptiles, amphibians, fishes, 439. Insects, 

 crustaceans, mollusca, echinoderms, coelenterates, 440. 



SECTION V 



Tlie Liver and its Function. 



Position and structure of liver, 440. Its four systems of tubes, 441. 

 Threefold function, 442. Glycogeny, 443. Proof of, 444. Origin of 

 glycogen threefold, 445. The use of glycogen as fuel, 447. Diagram 

 illustrating the process of change, 448. Cause of diabetes, 449. Com- 

 parative morphology of liver, 450. 



CHAPTER V. 



TEGUMENTARY ORGANS — SKIN STRUCTURES. 



SECTION I. 



Vertebrates. 



Structure of vertebrate skin, various changes in epidermis, 452. 

 Importance in classification, hair, 453. Nails, claws, 454. Hoofs, 

 horns, 455. Feathers, 456. Structure of feathers, adaptation to flight, 

 457. Mode of formation of feathers, gradation to hairs, 458. Scales, 

 459. Classification of fishes by scales, 460. Reptile scales, rattle of 

 rattlesnake, 461. Turtle shell, 462. Mammalian shell. Endoskeleton 

 and exoskeleton, 463. 



SECTION II. 



Invertebrates. 



Insect shell, 463. Higher crustaceans, 464. Mollusca : Bivalves, 

 growth of shell, 464 ; gastropod, cephalopod, classification of mollusca 

 by shell, 465. Echinoderms, structure of the shell, 466. 



Corals, 466. Structure of, 467. Structure and mode of formation 

 of the theca, 468. Sponge, skeleton of, 469. Rhizopod shell, 470. 



