4^8 CHORDATE ANATOMY 



osculum. A minute aperture. 



osmosis. The passage of dissolved substances of different concentration through a 



semipermeable membrane which separates them. 

 ossification. The formation of bone. 

 osteoblast. A bone-secreting cell. 



ostium tubae. The opening of the oviduct or uterine tube into the body cavity. 

 otic. Pertaining to the ear. 

 otoconia (or otoliths). Crystals of calcium carbonate contained in the endolymph of 



the membranous ear. 

 ovariotomize. To remove an ovary or ovarian tumor. 

 oviduct. The egg duct or uterine tube. 

 oviparous. Egg-laying. 



ovulation. The discharge of an egg from the ovary. 

 oxytocin. A pituitary hormone which affects the uterine muscle. 



pabulum. Food. 



Pacini's corpuscles. Large tactile corpuscles with single dendrite and many-layered 



capsule. 

 palate. The roof of the mouth — hard and soft. 



palatine. The membrane bone which forms the posterior part of the hard palate. 

 paleocortex. The primitive corte.x, or olfactory portion of the hemispheres. 

 paleontology. The science which treats of fossils. 

 paleostoma. The hj-pothetical primitive mouth of vertebrates — possibly represented 



in the hypophysial duct. 

 paleostriatum. The primitive corpus striatum (basal ganglion) as distinguished from 



the Epi- and Neostriatum. 

 paleozoic. The ancient life era from the Cambrian to the Permian period. 

 pallium. The cerebral cortex or layer of gray matter which covers the cerebral 



hemispheres. 

 pancreas. A combined digestive and endocrinal gland between stomach and duodenum. 

 panniculus camosus. A layer of integumentary muscles represented in man by the 



platysma of the neck. 

 papilla. A small nipple-shaped elevation. 



parachordal. A cartilage which lies along the anterior end of the notochord. 

 paracone. The anterior external cusp of an upper molar tooth. 

 paraconid. The anterior cusp of a lower molar tooth, 

 paradidymis. A rudiment of the mesonephros near the testis. 

 paraphysis. A hollow outgrowth of the anterior dorsal roof of the diencephalon. 

 parapodium. One of the paired appendages of annelids. 

 parapophysis. A transverse process from the centrum of a vertebra. 

 parasite. An organism which depends upon another for its living without paying 



board. 

 parasphenoid. A membrane bone of the roof of the mouth of fishes and amphibia, 

 parasympathetic. The craniosacral portion of the autonomic nervous system. 

 parathyroid glands. Ductless glands, usually four, which lie near the thyroids. 

 parietal organ (eye). The anterior epiphysial outgrowth from the diencephalon. 

 paroophoron. A rudiment of the mesonephros near the mammalian ovary. 

 parotid. The serous salivary gland below the ear. 

 patella. The knee-pan. 



pecten. A comb-like structure in the vitreous body of the eyes of reptiles and birds. 

 pectoral. Pertaining to the chest. 

 pedal. Pertaining to the foot. 



