^80 HUMAN PHYSIOLOGY. 



Motor nerve to facial muscles: portio dura, facial, or seventh pair. 



Motor nerve to tongue: hypoglossal, or twelfth pair. 



Motor nerve to laryngeal muscles: spinal accessory, or eleventh pair. 



Sensory nerve of the face: trigeminal, or fifth pair. 



Sensory nerves of the pharynx: glosso-pharyngeal, or ninth pair. 



Sensory nerves of the lungs, stomach, etc.: pneumogastric, or tenth 



pair. 



Length of spinal cord: 16 to 18 inches; weight, i l / 2 ounces. 

 Point of decussation of motor fibers: at the medulla oblongata. 

 Point of decussation of sensory fibers: throughout the spinal cord. 

 Function of anterolateral column of spinal cord: transmit motor 



impulses from the brain to the muscles. 

 Function of the posterior columns: assist in the coordination of 



muscular movements. 

 Function of the medulla oblongata: controls the functions of in- 



salivation, mastication, deglutition, respiration, circulation, etc. 

 Function of the cerebellum: center for the coordination of muscular 



movement. 



Function of the cerebrum: center for intelligence, reason, and will. 

 Center for articulate language: third frontal convolution on the left 



side of cerebrum. 

 Number of coats to the eye: three: ist, cornea and sclerotic; 2d, 



choroid ; 3d, retina. 



Function of iris: regulates the amount of light entering the eye. 

 Function of crystalline lens: refracts the rays of light so as to form 



an image on the retina. 



Function of retina: receives the impressions of light. 

 Function of membrana tympani: receives and transmits waves of 



sound to internal ear. 

 Function of Eustachian tube: regulates the passage of air into and 



from the middle ear. 

 Function of semicircular canals: assist in maintaining the equipoise 



of the body. 

 Function of the cochlea: appreciates the shades and combinations of 



musical tones. 



Size of human ovum: T |^ of an inch in diameter. 

 Size of spermatozoa: U L^ of an inch in length. 

 Function of the placenta: acts as a respiratory and digestive organ 



for the fetus. 

 Duration of pregnancy: 280 days. 



