APPENDIX III 377 



PERINEUM (G. perineon (?)), the pelvic region including the digestive and 



urinogenital outlets. 

 PERIPHERAL (G. pei'i, ai'ound, plus phero, to bear), that which lies near the 



margin, away from the center; the peripheral nerves, in distinction 



from the central nervous system. 

 Perissodactyl.\ (G. perissos, odd, plus daktylos, digit), an order of 



herbivorous mammals, including the horse, rhinoceros, zebra, etc. 

 PERITONEAL (G. peri, plus teino, to stretch), the membrane covering the 



intestines and mesenteries, and lining the body cavities. 

 Permian (from Perm, a province of Russia), a geological period including 



the most recent strata of the Paleozoic Era; it is followed in suc- 

 cession by the Triassic Period of the Mesozoic. 

 PETRO (G. petros, rock), a combining form; petrosal, Petromyzon. 

 Petromyzon (G. petros, plus myzon, sucker), a genus of lampreys. See 



Petromyzontia. 

 Petromyzontia (from Petromyzon, the type genus), a sub-class of cyclo- 



stomes, including the lamprej's. 

 PHAG (G. to eat), a combining form; that which eats, as phagocj'te. 

 pharyngeal (G. pharynx, throat), the region of the digestive tract be- 

 tween the mouth cavity and the esophagus; the region from which 



the gill pouches develop. 

 PHYLOGENY (G. pliyloii, tribe, plus genesis, beginning), the history of a 



race; opposed to ontogeny; phylogenetic is the adjective. 

 PHYLUM (G. phylon, tribe), a large group of animals or plants; a major 



division of a kingdom; the Phylum Chordata. 

 PHYSOS (G. a bubble, from phyo, to grow), a combining form; epiphysis; 



hj'pophysis. 

 pia (L. tender), the more deHcate membrane covering the brain, carrying 



blood vessels; pia mater. 

 pineal (L. pinea, a pine cone), an endocrine gland on the dorsal side of 



the diencephalon. See epiphysis. 

 pinna (L. feather), a wing or fin; specifically, the external ear. 

 Pisces (L. plural of piscis, fish), a class of vertebrates, the fish. 

 Pithecanthropus (G. pithekos, ape, plus anthropos, man), a genus of 



extinct, ape-hke men; the fossilized remains having been found in 



Java. P. erectus. 

 Pituitary (L. pituitarius, from pituiia, phlegm), an endocrine gland of 



the brain, derived partly from the diencephalon and partly from a 



stomodeal invagination. 

 PLACENTA (L. a cake, in reference to its discoidal shape), an embryonic 

 organ of the placental mammals, forming the embryonic attachment 

 to the uterine wall. 

 PLANTIGRADE (L. plantn, sole of foot, plus gradior, to walk), referring to 

 animals which walk with the sole of the foot on the ground; humans 

 or bears. 

 Pleistocene (G. pleistos, much, plus kainos, new), the most recent 



geological period, the uppermost strata of the Cenozoic. 

 Plesiosauria (G. pleistos, much, plus sauros, lizard), an order of extinct, 



aquatic reptiles. 

 pleura (G. side), a combining form; metapleural; pleural cavities. 

 plexus (L, interweaving), a group of interlacing or anastomosing nerves 

 or blood vessels. 



