NOTES. 385 



ratus in the head, is powerful enough to pulverize not only grain, but even 

 pieces ef glass and metal. This is done by two hard muscles moving obliquely 

 upon each other, aided by gravel purposely swallowed by thr bird. The 

 grinding may be heard by means of the stethoscope. 



51 Chyle is opaque in carnivores; more or less transparent in all other Ver- 

 tebrates, as in Birds, since the food does not contain fatty matter. 



5ia In Fishes, the villi are few or wanting. In Man, they number about 

 10,000 to the square inch. 



52 Except, perhaps, the tendons, ligaments, epidermis, etc. 



53 The phenomenon produced by these properties conjointly, capillary at- 

 traction and diffusion, is called endosmosis. 



54 The blood is colorless also in the muscular part of Fishes. That of 

 Birds is of the deepest red. The coloring matter of the red blood in worms 

 is not in the corpuscles, but in the plasma. 



55 Coagulation may be artificially arrested by common salt. Arterial blood 

 coagulates more rapidly than venous. The disposition of the red corpuscles 

 in chains, or rouleux, does not occur within the blood-vessels. The cause 

 has not been discovered. 



56 The corpuscles of Invertebrates are usually colorless, even when the 

 blood is tinged. 



57 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 composed of col- 

 orless corpuscles, showing their use in repairing injuries. 



58 There are no valves in the veins of Fishes, Reptiles, and Whales, and 

 few in Birds. 



39 Capillaries are wanting in the epidermis, nails, hair, teeth, and cartilages. 

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

 the blood, like other tissues, but is shed. 



60 A part of the blood, however, in going from the capillaries to the heart, 

 is turned aside and made to pass through the liver and kidneys for purifica- 

 tion. This is called the portal circulation, and exists in all Vertebrates ex- 

 cept that in Birds and Mammals it is confined to the liver. 



61 Two in the higher Mammals, three in the lower Mammals, Birds, and 

 Reptiles. They are called vence cavce. 



62 Tricuspid in Mammals, triangular in Birds. 



63 The pulse of a Hen is 140 ; of a Cat, 110 to 120; of a Dog, 90 to 100; 

 and of an Ox, 25 to 42. 



64 The bivalve Brachfopods breathe by delicate arms about the mouth, and 

 by the " mantle." 



65 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. 



66 In the human lungs they number 600,000,000, each about -^ of an 

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



25 



