388 GLOSSARY 



Pulmonary circulation : the circulation of the blood from the right 



ventricle of the heart through the pulmonary arteries, capillaries, 



and veins back to the left auricle. 



Pu'pil (Lat. pupilld) : the round opening in the center of the iris. 

 Pu-tre-fac'tion (Lat. putrefactio)i the offensive decay of albuminous 



and other matter. 

 Py-lo'rus (Gr. puloros, gate keeper) : the opening from the stomach 



into the intestine. 



Ra'di-ant energy (Lat. radiare, to emit rays) : the force resident in 

 vibrations of the ether which fills all space. 



Ra'di-us (Lat., a staff, rod, ray) : one of the bones of the forearm. 



Rec'tum (Lat. rectus, straight) : the last division of the large intes- 

 tine, and hence of the alimentary canal. 



Re'flex action (Lat. reflectere, reflexus, to bend back) : action in 

 which afferent impulses reach a nerve center and efferent impulses 

 are sent back without the higher brain centers having been stimu- 

 lated. Such action is involuntary and often unconscious. 



Re-frac'tion (Lat. refranyere, refractus, to break) : the change in 

 the direction of a ray of light in passing from one medium to an- 

 other of a different density. 



Re'nal (Lat. renes, kidneys) : pertaining to or in the region of the 

 kidneys, as the renal artery, the renal plexus. 



Ren'nin (Anglo-Saxon rinnan, to run): that ferment in the gastric 

 juice which causes milk to curdle ; the element in rennet which 

 assists in the making of cheese. 



Re-pro-duc'tion (Lat. reproduce re, to produce again) : the process by 

 which new organisms are produced from those already existing. 



Res'o-na-ting cavities (Lat. resonare, to sound back, echo) : the 

 pharynx, mouth, and nasal cavities, slight changes in which 

 modify the sound of the voice. 



Res-pi-ra'tion (Lat. respirare, to breathe) : the act of taking in and 

 giving out air. 



Re-spir'a-to-ry center : that cluster of nerve cells in the medulla ob- 

 longata which controls and coordinates the movements of the 

 muscles concerned in breathing. 



Ret'i-na (Lat. rete, a net) : that membrane of the eye in which the 

 fibers from the optic nerve terminate. 



Rhyth'mic (Gr. rhuthmos, measured motion) : characterized by a regu 

 lar succession of movements, impulses, or sounds. 



