PLASTIDIUM 



types the synonymy of which is given by Goodale 

 follows : — 



1114 



as 



P., Connective-tissue, the connective-tissue cor- 

 puscles. 



Plastidium (plas-tid' -e-uni) [dim. of tt?mot6<;, formed : 

 //., Plastidia\ The cell, or plastid, considered with 

 reference to its evolutionary or developmental possi- 

 bilities. See Plastid. 



Plastidular (plas-tid'-u-lar) [tvIclotos, formed]. Per- 

 taining to plastidules. 



Plastidule (pins' -tid-ul) [nTiaardq, verbal adj. of n?ida- 

 oeiv, mold, form]. In biology: (a) a protoplasm-mole- 

 cule ; (b) a term proposed by Elsberg as a substitute 

 for gemmule as used by Darwin. .See Heredity, Gem- 

 mule, Biophor, Pangene, Plasome. P. of Elsberg, the 

 ultimate physical units of living matter. See Heredity. 



Plastilytic (plas-til-it'-ik) [-rrXaoTog, molded; ?,i>eiv, 

 to dissolve]. Diminishing plasticity, or tending to 

 soften plastic materials. 



Plastin (plas'-tin) [rrXaordg, verbal adj. of nx7.aacsuv , 

 to form, mold]. In biology, one of the nucleins or 

 special nitrogenous proteids more insoluble in alkalies 

 and poorer in phosphorus than others ; called cytoplasm 

 by Schwartz. Cf. nuclei//, histon, adenin. 



Plastocolysis (plas-to-kol'-is-is) \jr\aar6q, molded; 

 auTivaig, hindrance]. Arrest of development. 



Plastodynamia (plas - to - di - nam' - e - ak) [n?Lacrr6(;, 

 molded ; fivvaiug, power]. Nutritive plastic power. 



Plastodynamic (plas-to-di-nam' '-ik) [jrAaoToq, molded ; 

 dbvautc, force]. Pertaining to nutritive power. 



Plastoprolepsis ( plas-to-pro-lep' -sis) \jrAaardc, molded ; 

 Tcpd/./jipiq, anticipating]. Premature development of 

 an organ or part. 



Plastral (plas'-tral) [plastron, a breast-plate]. In 

 biology, of or pertaining to the plastron, q. v. 



Plastron (plas'-tron) [Fr., "breastplate"]. The 

 sternum and costal cartilages, with the attached parts, 

 such as are removed when a post-mortem examina- 

 tion is made of the condition of the thorax. In biology : 

 (a) the ventral portion of the exo-skeleton of a 

 tortoise or turtle ; (b) one of the similar ventral, exo- 

 skeletal plates of certain amphibia ; (c) the ventral 

 shield of the fossil armadillo ; (d) a colored area on 

 the ventral surface of a bird. 



Plastrum (plas'-trum) [an accom. form of plastron, 

 a breastplate : pi., Plastra~\. Same as Plastron. 



Plate (plat) [ME., plate, a plate]. The horizontal 

 plate of the ethmoid bone constituting the floor of 

 the olfactory fossa and perforated for the passage 

 of the olfactory nerves. P., Abdominal. See 

 P., Lateral Mesoblastic. P., Ambulacral, one 

 of the coronal plates of a sea-urchin, which are 

 perforated to form part of an ambulacrum. P., Ap- 

 proximation, one of the plates of decalcified bone 

 or other material, leaving a central hole and openings 

 for sutures in the margin, which are used in enter- 

 ectomy to bring the resected ends of intestine to- 

 gether. Also known as Senn's Plate. P., Audi- 

 tory, the plate of bone forming the roof of the 



PLATE 



auditory meatus. P., Axial, the primitive streak of 

 the embryo. P., Basilar, P., Basicranial, in em- 

 bryology, the cartilaginous plate at the anterior end 

 of the notochord, formed by the latter and the para- 

 chordal cartilages. P., Blood. See Blood-plaque. 

 P.. Bone. Synonym of P., Approximation. P., 

 Branchial, one of the branchial arches of the em- 

 bryo. P., Cathammal, in biology, one of the 

 vascular lamellae of certain Medusa, formed by the 

 pressing together of the two layers of the persistent 

 endoderm by the subumbrellar and exumbrellar jelly. 

 P., Cribriform, the anterior fossa of the base of the 

 skull. P. -culture, in biology, a method devised by 

 Koch to separate bacteria by pouring the liquid, gelatin 

 culture-medium upon a sterilized glass plate, after 

 inoculation. The plates of Koch have been replaced 

 somewhat by Petri's Dishes, q.v. P.. Dorsal, each of 

 the two longitudinal ridges on the dorsal surface of the 

 embryo, which subsequently join to form the neural 

 canal. P., Electric, the finely granular end-plates 

 composed of nerve-endings and large cells, found in 

 the electric organs of electric fishes. P., End, a 

 term given to the termination of a motor nerve in a 

 muscle-fiber. P., Equatorial, in biology, the com- 

 pressed mass of chromatic segments, aggregated about 

 the equator of the nuclear spindle at a certain stage 

 of karyokinesis. It is also called nuclear plate, nuclear 

 disc, mother-star. Ps., Facial, the fronto-nasal and 

 external group of nasal and maxillary plates of the 

 embryo. P., Flesh. See Lamella carnosa. P., 

 Foot, the flat, plate-like portion of the stapes which 

 fills the fenestra ovalis. P., Frontal, in the fetus, a 

 cartilaginous plate interposed between the lateral par's 

 of the ethmoid cartilage and the lesser wings and 

 anterior portion of the sphenoid bone. P., Fronto- 

 nasal, the middle of the facial plates, which subse- 

 quently forms the external nose. P., Gill, a bronchial 

 lamina of molluscs. P., Gray. Synonym of Lamina 

 cinerea. P., Ground, the ground-substance of con- 

 nective tissue and endothelial cells, in which are cm 

 bedded the nucleus and intracellular network. P., 

 Hair. Synonym of Scales, Hair. Ps., Hyoid, the 

 second pair of the subcranial plates of the embryo, 

 from which the hyoid bone is in part developed. P., 

 Inferior Maxillary, in the embryo, the first pair of 

 subcranial plates from which the mandible is developed. 

 P., Internasal. Synonym of P., Fronto-nasal. P.. 

 Intervertebral, the disc of fibro-cartilage between 

 adjacent vertebras. P., Intrafissural (of th 

 the fold of pia passing into the ventral fissure of the 

 spinal cord. P., Lateral Mesoblastic, the thic 

 portion of the mesoblast situated one on each side <>l 

 the notochord. Each plate splits into two portions, 

 the ectal divisions coalescing to form the body-wall, or 

 So/natopleure , the ental, to form the Splanchnop 

 visceral covering. P., Ligamentous, one of 

 intervertebral fibrous discs of the embryo. P., Man- 

 dibular. Synonym of P., Lnferior Maxillary. P-i 

 Maxillary. Synonym of P., Inferior M 

 P., Medullary. Synonym of P. , Dorsi 

 Mesenteric, P., Mesentery, P., Mesial. ^ 

 onyms of P., Lateral Mesoblastic. P., Motor. Syn 

 onym of P., End. P., Muscle, P., Muscular. 

 See Myocomma. P., Negative, of a st> 

 that plate which by the action of the changin| 

 current is partly covered with a coating of spong) 

 lead; of a voltaic cell, that element of a voltai 

 couple which is negative in the electrolyte of the cell. 

 P., Nuclear. Synonym of P., Equatorial. 

 Orbital: (i) the smooth plate of the ethmoid bon< 

 forming part of the inner wall of the orbit ; (2) of t 

 frontal bone, a horizontal plate forming the roof of the 



