PHYSIOLOGIC CONSTANTS 305 



Motor nerves to eyeball and accessory structures: Motor oculi, or third 



pair; pathetic, or fourth pair; abducens, or sixth pair. 

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

 Motor nerve to tongue: Hypoglossal, or twelfth pair. 

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

 Sensory nerve of the pharynx: Glossopharyngeal, or ninth pair. 

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

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

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

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

 Function of the anterolateral columns of the spinal cord: Transmit motor 



impulses from the brain to the muscles. 

 Functions of the posterior columns: Assist in the co-ordination of muscular 



movements. 

 Functions of the medulla oblongata: Controls the functions of insalivation, 



mastication, deglutition, respiration, circulation, etc. 

 Function of the cerebellum: Center for the co-ordination of muscular 



movements. 



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

 Center for articulate language: Third frontal convolution on the left side 



of the cerebrum. 

 Number of coats to the eye: Three first, cornea and sclerotic; second, 



choroid and iris; third, 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 impression of light. 

 Function of the membrana tympani: Receives and transmits waves of 



sound to the internal ear. 

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



from the middle ear. 

 Function of the 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 | 7 inch in diameter. 

 Size of spermatozoon: ^ inch in length. 

 Function of placenta: Acts as a respiratory and digestive organ for the 



fetus. 

 Duration of pregnancy: Two hundred and eighty days. 



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