576 GLOSSARY 



periosteum (p6r I 6s' t6 iim). A fibrous membrane covering a bone; adj., periosteal. 



peristalsis (p6r I star sis). A succession of rhythmical contractions of tlie wall of 

 the intestine, or other muscular tubes, which drives the contents onward; adj., 

 peristaltic. 



peritoneum (p6r I to ne' um). The membrane lining the coelomic cavity; in mammals 

 limited to the abdominal cavity; adj., peritoneal. 



Pfliiger, Eduard. German physiologist; 1829-1910. 



phag (faj). G.; eat. 



phagocyte (fSg' 6 sit). A leucocyte when engaged in the engulfing and destruction of 

 other cells or various foreign objects. 



pharynx (far' inks). A region of the alimentary canal between the mouth cavity and 

 the esophagus; adj., pharjTigeal (fa rin' je al). 



phenotype (fe' no tip). A type of organism considered as a complex of visible char- 

 acters; adj., phenotypic (fe no tip' Ik). 



phore (for). G.; bearer. 



photo (f 5' 1 6). G.; light. Photic (fo' tik). Pertaining to light. 



photosynthesis (fo t6 sin' the sis). The production of carbohydrates from carbon 

 dioxide and water by chlorophyll, using the energy of sunlight. 



phototropism (fo t5t' r6 piz'm). The response of an organism to light; adj., photo- 

 tropic (fo to tr6p' Ik). 



phyl (fil). G. ; race, or tribe. 



phylogeny (fil6j'6nl). The series of stages passed through in the evolution of a 

 group of animals; adj., phylogenic (fi 16 j6n' Ik) or phylogenetic. 



physiological state. A condition of an organism at any given time which is the 

 resultant of the metabolic processes that have preceded and which determines the 

 manner in which the organism will respond to stimulation. 



phyt (fit). G.; plant. 



pia mater (pi' a ma' ter). A delicate connective tissue membrane closely adherent 

 to the spinal cord and brain of vertebrates. 



pineal (pin' g al) body. A dorsal outgrowth of the diencephalon in vertebrates; it 

 probably served as an eye in primitive vertebrates now extinct and remains as a 

 rudimentary structure in living forms, in some of which it may function as an 

 endocrine gland. Also called pineal eye and pineal gland. 



pituitary (pi tti' I ta rl) body. A ventral outgrowth of the diencephalon in verte- 

 brates, to which is added tissue from a dorsal outgrowth of the mouth cavit}^; it 

 functions in many forms as an endocrine gland. 



placenta (pla s6n' ta). An organ by which the young of a mammal becomes attached 

 to the wall of the maternal uterus and through which it receives food and oxygen 

 and disposes of waste; it is derived in part from the chorion of the embryo, in 

 some cases including the allantois, and in part from the uterine wall; adj., 

 placental. 



plankton (plank' t6n). That part of a pelagic fauna made up of small and weak 

 organisms which are at the mercy of winds and waves. 



piano (pla' no). L.; flat. 



plasm (plaz'm). G.; anything formed; in biology, living matter. 



plasma (phiz' ma). The liquid part of the blood. 



plasma membrane. A living membrane on a cell, as distinguished from a nonliving 

 cell wall. 



plasmosome (plaz' mo som). A nucleolus not composed of chromatin. 



plast (plast). G. ; an organized particle or granule, including a cell. 



plastid (plas' tid). A body in the cytoplasm of a cell carrying on some constructive 

 chemical process, as the chlorophyll bodies, or chloroplasts. 



platy (pla' tl). G.; flat, broad. 



