LAWN-TENNIS ARM 



665 



LEAD 



appearance of kathelectrotonus and the disap- 

 of anelectrotonus — not, however, by the 

 ppearance of kathelectrotonus, or by the appear- 

 of anelectrotonus." L. of Progress, the law 

 f progressive increase in the perfection of organisms 

 the successive periods of the earth's history. L., 

 sycho-physical. See L., Fechner's. L. of Re- 

 rocal Proportions, two elements combining with 

 third do so in proportions that are simple multi- 

 or simple fractions of those in which they com- 

 e with each other. L. of Refraction, that rays 

 light entering a denser medium are deflected toward 

 perpendicular drawn through the point of incidence, 

 d those entering a rarer medium are deflected away 

 m the same perpendicular. L., Ritter's or Ritter- 

 alli's, if a nerve be separated from its center, or if 

 center die, the excitability of the nerve is in- 

 •ased: the increase of excitability begins at the 

 tral end, and travels towards the periphery ; the 

 citability then falls until it disappears entirely. L. 

 Sexual Transmission, a parent transmits charac- 

 tics to children of his or her sex not transmitted to 

 opposite sex. L., Stokes' : I. See Z., Angstrom's. 

 Every muscle in relationship with an inflamed 

 cous or serous surface becomes paralyzed. L., 

 ait's, in every disease of the abdomen or pelvis in 

 ich the health is destroyed or life is threatened, and 

 which the condition is evidently not due to malig- 

 t disease, an exploration of the cavity by celio- 

 ;omy should be made. L., Toynbee's, a law con- 

 cerning intracranial disease secondary to otitis. It 

 is that the cerebellum and lateral sinus suffer from 

 disease of the mastoid, while the cerebrum is endan- 

 gered by caries of the tympanic roof. L., Valli- 

 Ritter's. See L., Ritter-VallV s. L., Van der 

 Kolk's, the sensory fibers of a mixed nerve are dis- 

 tributed to parts that are moved by muscles that re- 

 ceive the motor fibers of the same nerve. Thus, in 

 nerve-lesions the chief sensory symptoms are always 

 peripheral or distal from the chief motor symptoms. 

 , Volta's, of Tension, the contact of two differ- 

 t substances produces an electromotive force equal 

 the algebraic difference of their electric condition, 

 which difference is constant for the same substances. 

 L., Vulpian's, the functions of a destroyed portion 

 of an animal's brain are assumed by the remaining 

 portion. L., Wallerian, of Degeneration; from 

 periments Waller showed that the trophic centers of 

 e ventral roots of spinal nerves lie in the multipo- 

 nerve-cells of the ventral horns of gray matter, 

 while those of the dorsal roots lie in the ganglia placed 

 upon them. Generalized, the law predicates that 

 the course of the impulses in a nerve may be ascer- 

 tained by tracing the course of the subsequent degen- 

 eration. L., Weber* s, the principle that that varia- 

 tion of stimulus that causes the smallest appreciable 

 variation in sensation maintains, approximately, a 

 fixed ratio to the total stimulus. See also Z., 

 Fechner ' s. 

 Lawn-tennis Arm. Displacement of the tendon, or 

 body (or both) of the pronator radii teres. Com- 

 mon in lawn-tennis players. L.-t. Knee. See Knee. 

 L.-t. Leg, tendinous, fascial, or muscular rupture 

 in the calf or sura. 

 Lawsonia /aw-so'-ne-ah). See Henna. 

 Lax (laks) [laxus, loose]. Loose ; not tense. 

 Laxarthrus (laks-ar* -thrus) [laxus, loose; apdpov, 



joint]. Luxation of a joint. 

 Laxative {laks' -at-iv) [laxativus ; laxare, to loosen]. I. 

 rient ; mildly cathartic. 2. An agent that loosens 

 the bowels ; a mild purgative. 

 Laxator [laks-a' -tor) [laxare, to^loosen]. That which 



pe 



loosens or relaxes. A name applied to various mus- 

 cles. L. tympani. See Muscles, Table of. 



Laxitas {laks'-it-as) [L.]. Looseness. L. alvi, diar- 

 rhea. L. gingivarum, spongy gums. L. intes- 

 tinorum, diarrhea. L. ventriculi, atony of the 

 stomach. 



Laxity (laks'-it-e) \laxitas, looseness]. Lack or loss 

 of tone or tension ; a relaxed, loose, or spongy state of 

 a tissue. 



Layer (la'-er) [ME., leyer, a layer]. A mass of uni- 

 form, or nearly uniform, thickness, spread over or 

 covering a considerable area. L., Bacillar (of the 

 retina), the layer of rods and cones of the retina. L., 

 Basement, basement membrane, q. v. L., Bow- 

 man's. See Lamina, Bo~u-man's. L., Fibrous [of the 

 pericardium), the outer layer of the pericardium, con- 

 tinuous above with the deep cervical fascia. L., Funda- 

 mental, one of the three layers of the blastoderm, q. v. 

 L., Ganglionic, a layer of angular cells of the cerebral 

 cortex, best developed in the motor area. L., Ger- 

 minal. See L., Fundamental. L., Henle's, the 

 outer layer of the inner root-sheath of the hair. L*, 

 Huxley's, the inner layer of the inner root-sheath of 

 the hair. L., Horny (of the epiderm), the superficial 

 layer of the skin. L., Inner Molecular, one of the 

 layers of the retina. L., Latticed, the formatio reticu- 

 laris, q. v. L., Malpighian, the rete mucosum of 

 the skin. L., Ollier's. See Z., Osteogenetic. L., 

 Osteogenetic, the lower layer of periosteum, con- 

 nected with the formation of bone. L., Papillary (of 

 the skin), the upper layer of the true skin, having papil- 

 lary projections fitting into the epidermis. L., Pig- 

 mentary (of the retina), the innermost layer of cells 

 of the retina extending also to the choroid, ciliary body, 

 and iris. L., Primitive, or Primordial, the layers of 

 the blastoderm ; by some applied to epiblast, hypo- 

 blast, and mesoblast ; by others to the first two only. 

 L. of Rods and Cones. See Z., Bacillar, and 

 Retina. L., Serous, the ental layer of serous mem- 

 branes, consisting of endothelium. 



Layering (la f -er-ing) [ME., leyer, a layer]. The 

 propagation of plants by layers. 



Layette (lay-et') [Fr.]. The full outfit of garments, 

 bedding, etc. , for a new-bom child. 



Layman (la' -man) [D., leeman, a layman]. A mem- 

 ber of the laity. 



Lazar (ta'-zar) [from Lazarus, a Biblical name]. An 

 old name for a leper, or for any person having a repul- 

 sive disease. 



Lazaret Fever. A synonym of Typhus Fever, q. v. 



Lazaretto {laz-ar-ef -o) [Ital. , a pest-house]. A quar- 

 antine establishment. Also, a place for fumigation 

 and disinfection. 



Lazari malum (laz'-ar-i ma'-lum) [L., "Lazarus' 

 ill'']. Synonym of Leprosy. 



Lazulite (laz'-u-tit) [S., azul, blue]. A mineral of a 

 light-blue color, composed of the hydrous phosphate 

 of aluminum, magnesium, and iron. 



Leaching (lich'-ing) [ME., leechen, to wet]. In 

 chemistrv, removing bv percolation. 



Lead (led) [ME., leed, lead]. See Plumbum. L., 

 Black. See Graphite. L.-colic. See Colic. L.- 

 encephalopathy, a morbid condition of the brain due 

 to chronic lead-poisoning. L.-line, blue line ; the line 

 of discoloration on the gums in cases of chronic lead- 

 poisoning. L. -pipe Contraction, Weir Mitchell's term 

 for the marked resistance encountered in attempting to 

 flex the legs in cases of spastic paraplegia of infants, 

 the resistance gradually yielding as the effort to flex is 

 maintained ; also the condition of the limbs in the 

 cataleptic state in which they maintain any position 

 that is given them. L.-pipe Paralysis. Same as 



