GLOSSARY. 261 



PRES-BY-O'PI-A (Gr. TtpsdfiVs, presbuS) old, and GJI/>, ops, the eye). 

 A defect of the accommodation of the eye, caused by the harden- 

 ing of the crystalline lens ; the " far-sight" of adults and aged 

 persons. 



PJIOC'ESS (L. proce'do, proces'sus, to proceed, to go forth). Any pro- 

 jection from a surface. Also, a method of performance ; a pro- 

 cedure. 



PTY'A-LIN (Gr. itrvaXov, ptualon, saliva). The peculiar organic 

 ingredient of the saliva. 



PUL'MO-NA-RY (L. pul'mo, pulmo'nis, the lungs). Pertaining to the 

 lungs. 



PULSE (L. pel'lo, pul'sum, to beat). The striking of an artery against 

 the finger, occasioned by the contraction of the heart, commonly 

 felt at the, wrist. 



PU'PIL (L. pupil'la). The central, round opening in the iris, through 

 which light passes into the depths of the eye. 



PY-T>O'RUS (Gr. 7tvha)p6's, puloros, a gate-keeper). The lower open- 

 ing of the stomach, at the beginning of the small intestine. 



RE'FLEX ACTION. An involuntary action of the nervous system, by 

 which an external impression conducted by a sensory nerve is 

 reflected, or converted into a motor impulse. 



RES-FI-RA'TION (L. res'piro, to breathe frequently). The function 

 of breathing, comprising two acts : inspiration, or breathing in, and 

 expiration, or breathing out. 



HET'I-NA (L. re'te, a net). The innermost, of the three tunics or coats 

 of the eyeball, being an expansion of the optic nerve. 



SAC'CHA-RINE (L. sac'cliarum, sugar). Of the nature of sugar; 

 applied to the important group of food substances which embraces 

 the different varieties of sugar, starch, and gum. 



SA-LI'VA (L.). The moisture or fluids of the mouth, secreted by the 

 salivary glands, etc. 



SCLE-ROT'IC (Gr. tiKXrjpoS, skleros, hard). The tough, fibrous outer 

 tunic of the eyeball. 



SE-BA'CEOUS (L. sebum, fat). Resembling fat , the name of tnc oily 

 secretion by which the skin is kept flexible and soft. 



SE-CRE'TION (L. secer'no, secre'tum, to separate). The process ol 

 separating from the blood some essential important fluid ; which 

 fluid is also called a secretion. 



SEM-I-CIR'CU-LAR CANALS. A portion of the internal ear. 



SEN-SA'TION. The perception of an external impression by the ner- 

 vous system ; a function of the brain. 



SEN-SI-BIL'I-TY, GENERAL. The power possessed by nearly aU parts 



