476 NOTES 



110 The corpuscles of invertebrates are usually colorless, even when the 

 blood is tinged. 



111 Except during the foetal life. The corpuscles of the camel are non- 

 nucleated, as in other mammals. If the transparent fluid from a boil be 

 examined with a microscope, it will be seen to be almost entirely composed 

 of colorless corpuscles. 



112 There are no valves in the veins of fishes, reptiles, and whales, and 

 few in birds. 



113 Capillaries are wanting in the epidermis, nails, hair, teeth, and carti- 

 lages. Hence, the epidermis, for example, when worn out by use, is not 

 removed by the blood, like other tissues, but is shed. 



114 A part of the blood, however, in going from the capillaries of the 

 digestive organs to the heart, is turned aside and made to pass through the 

 liver and kidneys for purification. This is called the portal circulation, 

 and exists in all vertebrates, except that in birds and mammals it is con- 

 fined to the liver. 



115 Two in the higher mammals, three in the lower mammals, birds, and 

 reptiles. They are called vena cava. 



116 Tricuspid in mammals, triangular in birds. 



117 The pulse of a hen is 140 ; of a cat, 1 10 to 120 ; of a dog, 90 to 100 ; 

 and of an ox, 25 to 42. 



118 The bivalve brachiopods breathe by delicate fringed arms about the 

 mouth, and by the " mantle. " 



119 The air bladder, found in most fishes, is another rudiment of a lung, 

 although it is used, not for respiration, but for altering the specific gravity 

 of the fish. In the gar pike of our Northern lakes it very closely resem- 

 bles a lung, having a cellular structure, a tracheal tube, and a glottis. It is 

 here functional. The gills represent lungs only in function ; they are totally 

 distinct parts of the organism. 



12) In the human lungs they number 600,000,000, each about T J 7 of an 

 inch in diameter, with an aggregate area of 132 square feet. The thickness 

 of the membrane between the blood and the air is ^Q^ of an inch. The 

 lungs of carnivores are more highly developed than those of herbivores. 

 In the manatee, they are not confined to the thorax, but extend down 

 nearly to the tail. 



121 Crocodiles are the only reptiles whose nostrils open in the throat be- 

 hind the palate, instead of directly into the mouth cavity. This enables 

 the crocodile to drown its victim without drowning itself ; for, by keeping 

 its snout above water, it can breathe while its mouth is wide open. 



122 A rudimentary diaphragm is seen in the crocodile and ostrich. 



123 The poison glands of venomous serpents and the silk vessels of cater- 

 pillars are considered to be modified salivary glands. Birds, snakes, and 

 cartilaginous fishes have no urinary bladder. 



124 Since the weight of a full-grown animal remains nearly uniform, it 



