HUMAN PHYSIOLOGY. 



into systems e. g. } the bones, collectively, constitute the bony or 

 osseous system ; the muscles, the nerves, the skin, constitute, respec- 

 tively, the muscular, the nervous, and the tegumentary systems. 



Physiologic Apparatus. More important from a physiologic point 

 of view than a classification of organs based on similarities of struc- 

 ture is the natural association of two or more organs acting together 

 for the accomplishment of some definite object, and to which the 

 term physiologic apparatus has been applied. While in the com- 

 munity of organs which together constitute the animal body each one 

 performs some definite function, and the harmonious cooperation of 

 all is necessary to the life of the individual, everywhere it is found 

 that two or more organs, though performing totally distinct func- 

 tions, are cooperating for the accomplishment of some larger or 

 compound function in which their individual functions are blended 

 e. g., the mouth, stomach, and intestines, with the glands connected 

 with them, constitute the digestive apparatus, the object or function 

 of which is the complete digestion of the food. The capillary blood- 

 vessels and lymphatic vessels of the body, and especially those in 

 relation to the villi of the small intestine, constitute the absorptive 

 apparatus, the function of which is the introduction of new material 

 into the blood. The heart and blood-vessels constitute the circulatory 

 apparatus, the function of which is the distribution of blood to all 

 portions of the body. The lungs and trachea, together with the 

 diaphragm and the walls of the chest, constitute the respiratory ap- 

 paratus, the function of which is the introduction of oxygen into 

 the blood and the elimination from it of carbon dioxid and other 

 injurious products. The kidneys, the ureters, and the bladder con- 

 stitute the urinary apparatus. The skin, with its sweat-glands, con- 

 stitutes the perspiratory apparatus, the functions of both being the 

 excretion of waste products from the body. The liver, the pancreas, 

 the mammary glands, as well as other glands, each form a secretory 

 apparatus which elaborates some specific material necessary to the 

 nutrition of the individual. The functions of these different physi- 

 ologic apparatus e. g., digestion, absorption of food, elaboration of 

 blood, circulation of blood, respiration, production of heat, secretion, 

 and excretion are classified as nutritive functions, and have for 

 their final object the preservation of the individual. 



The nerves and muscles constitute the nervo-muscular apparatus, 

 the function of which is the production of motion. The eye, the 



