368 GLOSSARY. 



Pharynx (far'-ingks). The cavity back of the soft palate. It commu- 

 nicates anteriorly with the posterior nares, laterally with the eusta- 

 chian tubes, ventrally with the mouth, and posteriorly with the 

 gullet and larynx. 



Plasma {plaz'-ma}. The original undifferentiated substance of nascent, 

 living matter. The fluid part of the blood and lymph. 



Pleura (pld'-ra*). The serous membrane which envelops the lungs, and 

 which, being reflected back, lines the inner surface of the thorax. 



Plexus (plek'-sus). An aggregation of vessels or nerves forming an 

 intricate net-work. 



Pneumogastric (nu-mo-gas'-trik). Pertaining conjointly to the lungs 

 and the stomach, or to the pneumogastric or vagus nerve. 



Portal (por'-tal). Pertaining to the porta (gate) or hilum of an organ, 

 especially of the liver, as the portal vein. 



Postcaval (jwst-kd'-val). Pertaining to the postcava; the postcaval 

 vein, formerly called the inferior vena cava, or vena cava ascendens. 



Precaval (prv-ka'-val}. Pertaining to the precava; the anterior caval 

 vein, formerly called the superior vena cava, or vena cava de- 

 scendens. 



Pronation (pro-na'-shun). The turning of the palm downward. 



Protoplasm (pro'-to-plazm). An albuminous substance, ordinarily re- 

 sembling the white of an egg, consisting of carbon, oxygen, nitro- 

 gen, and hydrogen in extremely complex and unstable molecular 

 combination, and capable, under proper conditions, of manifesting 

 certain vital phenomena, such as spontaneous motion, sensation, 

 assimilation, and reproduction, thus constituting the physical basis 

 of life of all plants and animals. 



Ptyalin (tl'-a-lin}. An amylolytic or diastasic ferment found in saliva, 

 having the property of converting starch into dextrin and sugar. 



Pulmonary (pul'-md-na-ri}. Pertaining to the lungs. 



Pylorus (pl-lo'-rus). The opening of the stomach into the duodenum. 



Radius (ra'-dfi-ws). The outer of the bones of the forearm. 



Renal (re'-nal). Pertaining to the kidneys. 



Rennin (ren'-in). An enzyme, or ferment, to whose action is due the 

 curdling or clotting of milk produced upon the addition of ren- 

 net. 



Retina (ret'-i-na). The chief and essential peripheral organ of vision; 

 the third or internal coat or membrane of the eye, made up of the 

 end organs or expansion of the optic nerve within the globe. 



