VOCABULARY. 307 



Os hyoides, the bone of the tongue and throat. 



Os pubis, the bone which arches forward from the pelvis, and supports 



the lower part of the belly. 

 Ossification, a change of structure into bone. 

 Oviparous, bringing forth or bearing young by means of eggs. 



Palmated, having a palm like that of the hand. 



Pancreas, a gland within the abdomen, just below the stomach, and 



providing a fluid to assist in digestion. 

 Papillae, little projections on the surface of organs, as on the tongue, 



which are the seats of sensation. 

 Papilionaceous, of or resembling butterflies. Applied to a certain 



tribe of flowers on account of their resemblance in shape to those 



insects. 

 Pectoral, of or relating to the chest. 

 Pelvis, the broad flat basin, constituting the lower part of the abdomen, 



composed principally of the broad flat bones usually called the hip 



and haunch bones. 

 Peritonaeum, a membrane lining the cavity of the abdomen and giv- 

 ing a close coveiing to all its contents. 

 Peristaltic, applied to the crawling, worm-like motion of the intestines. 

 Pericardium, the bag containing the heart. 

 Pericarpium, a kind of seed vessels of plants. 

 Periosteiim, the membrane which adheres to, and closely invests the 



surface of bones. 

 Petals, the flower leaves, or leaves of the corolla of plants. 

 Pharynx, the cavity at the back part of the mouth which receives the 



food just before swallowing, and transmits it to the Oesophagus. 

 Phosphoric, of or resembling phosphorus. 

 Pistil, the part of a flower intended to receive the pollen or fertihzing 



dust of the stamens. 

 Piston, a moveable cylinder in the tube of some machines, intended 



to take off' by its motion the pressure of the air, or to receive the 



impulse from steam ; as in the pump and steam-engine. 

 Plantide, a little plant. Applied to the part which hrst sprouts from 



the seed when it begins to grow. It refers to the same part with 



Plumule. 

 Pleura, the membrane lining the chest. 

 Plumule, see plantule. 



Pneumatic, of or relating to the air or wind. 

 Pollen, the ^rtilizing dust of flowers, produced by the stamens and 



falling upon the pistils in order to render a flower capable of pro- 

 ducing seed or fruit. 

 Primordial, original. 



R. 



Radicle, the little root which is first sent out by a seed when it begins 



to grow. 

 Refraction, generally applied to the change of direction which takes 



place when a ray of light moves from one medium into another of a 



different density. 

 Renitency, resistance. 

 Retina, a very sensible and delicate membrane at the back part of the 



eye, intended to receive the images of objects like the scieen of a 



camera obscura. Supposed to be an expansion of the nerve of the eye. 

 Rictus, the extent of the mouth when opened widely as in gaping. 



