852 Appendix 



Porifera (po -rif era) (Gr. poros, pore; ferro, to bear), pore-bearing sponges. 



Portal vein (port' al) (L. porta, gate), blood vessel carrying blood to the liver 

 from spleen, pancreas, digestive tract, etc. 



Postcaval vein (post -ka' val) (L. post, after; cavus, hollow), inferior (posterior)' 

 vena cava carrying blood to the heart from posterior parts of the body. 



Posterior (pos -te' ri or) (L. posterior, following), behind or opposite anterior 

 (head). 



Potential energy (po -ten' shal) (L. potens, be able), stored energy possessed by 

 virtue of position or stresses, such as the stored energies of food, coal, 

 wood, etc. (contrast with Kinetic energy). 



Precaval vein (pre -ka' val) (L. prae, before; cavus, hollow), anterior (superior) 

 vena cava carrying blood to the heart from the anterior parts of the body. 



Precipitin (pre -sip' i tin) (L. praecipitare, precipitate), specific antibody devel- 

 oped in response to stimulation by a foreign protein and characterized by 

 causing a precipitation. 



Predaceous (pre -da' shus) (L. Praeda, prey), outright killing of an animal, such 

 as owls killing (preying on) mice, etc. 



Preformation (pre for -ma' shun) (L. prae, before), old theory that adults are 

 preformed (represented in miniature) in the germ cell (contrast with 

 Epigenesis). 



Premaxilla (pre max -il' a) (L. prae, before; maxilla), in front of the maxilla or 

 upper jaw. 



Prenatal (pre -na' tal) (L. prae, before; natalis, birth), before birth. 



Primates (pri' mate) (L. primus, first), highest animals such as man, apes, 

 monkeys. 



Primordial germ cell (pri -mor' di al) (L. primordium, origin), first cell set aside 

 in the embryo for future development of sex organs. 



Proboscis (pro -bos' is) (Gr. proboskis, trunk), trunklike process. 



Progestin (pro -gest' in), hormone of the corpus luteum (yellow body) of the ovary. 



Proglottid (pro -glot' id) (Gr. pro, for; glotta, tongue), one of the sections or 

 individuals of the chain making up a cestode worm such as tapeworm. 



Pronephros (pro -nef ros) (Gr. pro, before; nephros, kidney), first kidney struc- 

 ture to develop in a vertebrate. 



Prophase (pro' faz) (Gr. pro, before; phasis, to appear), preparatory stage of 

 mitosis preceding the metaphase. 



Prophylaxis (pro fy -lacks' is) (Gr. pro, before; phylasso, guard), preventive raieas- 

 ures in connection with diseases. 



Prosopyle (pros' o pile) (Gr. proso, forward; pyle, gate), pores leading into flagel- 

 lated chambers from the incurrent canals in certain sponges. 



Prostate (pros' tat) (Gr. pro, before; stare, stand), an accessory male reproduc- 

 tive gland near the urethra. 



Prostomium (pro -stom' i um) (L. pro, before; stoma, mouth), portion of head 

 before the mouth. 



Protective resemblance, protection of an organism due to the resemblance of it, 

 or some part of it, to its environment. This resemblance may be due to 

 structure, color, pattern, etc. 



Protein (pro'tein) (Gr. protos, first), compound of carbon, hydrogen, oxygen, 

 and nitrogen, and frequently traces of phosphorus or sulfur. 



