416 BIOLOGY 



ptyalin. The enzyme in saliva which converts starch into sugar. 



pubis, 182. 



puffballs, 245. 



pulmonary arteries (Gr. pkumon = a lung). Blood vessels carrying blood 



to the lungs, 191. 



pulmonary circulation. -The circulation through the lungs, 191. 

 pulmonary veins. The blood vessels carrying blood from the lungs to the 



heart, 191. 



pupa. A stationary, inactive stage between a larva and an adult, 289. 

 pupil. An opening in the center of the iris allowing light to enter the eye, 



197. 

 putrefaction. Decomposition of organic products, taking place without 



the presence of much oxygen, 81. 



pylorus. The opening of the stomach into the intestine, 186. 

 quadrate bones, 180. 

 quadrato-jugal bones, 181. 

 rabbit, skeleton of, 364. 

 race variations. Variations by which the race is gradually or suddenly 



modified, 338. 



racemose. Arranged somewhat like a cluster of grapes. 

 radiant heat. Heat which is given off from a hot body into space, 297. 

 radius, 182. 

 ramus. A branch. 



reaction. A response to an external stimulus, 43. 

 recapitulation theory. See repetition. 

 receptacle. In botany, the end of the flower peduncle on which the floral 



leaves are borne, 118. 

 recessive characters (Lat. recessus = receding). Characters which fail to 



appear in a first generation, but may appear in later generations, 



360. 



rectum. The enlarged, posterior end of the intestine, 186. 

 REDI, 12. 

 reflex action. An action produced by a stimulus passing to the central 



nervous system and there giving rise to stimuli which pass outward to 



the muscles, but without volition, 212. 



regeneration. The redevelopment of parts that have been lost, 150. 

 reintegrate. To recombine compounds that have been disintegrated. 

 renal.- - Pertaining to the kidneys. 

 renal portal vein. A vein from the legs of the frog that breaks up into 



capillaries in the kidney, 191. 

 repetition, law of. The law that the development of animals repeats their 



past history, 290. 



