LAWN-TENNIS ARM 



»;.;.-. 



LEAD 



the appearance of kathelectrotonus and the disap- 

 pearance of anelectrotonus — not, however, by the 

 disappearance of kathelectrotonus, or by the appear- 

 ance of anelectrotonus.'' L. of Progress, the law 

 of progressive increase in the perfection of organisms 

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

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

 ciprocal Proportions, two elements combining with 

 a third do so in proportions that are simple multi- 

 ples or simple fractions of those in which they com- 

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

 of light entering a denser medium are deflected toward 

 a perpendicular drawn through the point of incidence, 

 and those entering a rarer medium are deflected away 

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

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

 the center die, the excitability of the nerve is in- 

 creased; the increase of excitability begins at the 

 central end, and travels towards the periphery; the 

 excitability then /a/Is until it disappears entirely. L. 

 of Sexual Transmission, a parent transmits charac- 

 teristics to children of his or her sex not transmitted to 

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

 2. Every muscle in relationship with an inflamed 

 mucous or serous surface becomes paralyzed. L., 

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

 which the health is destroyed or life is threatened, and 

 in which the condition is evidently not due to malig- 

 nant disease, an exploration of the cavity by celio- 

 tomy 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 Z., Ritter-Valli's. L., Van der 

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

 tributed to parts i hat are moved by muscles that re- 

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

 nerve-lesions the chief sensory symptoms are always 

 peripheral or distal from the chief motor symptoms. 

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

 ent substances produces an electromotive force equal 

 to the algebraic difference of their electric condition, 

 which difference is constant for the same substances. 

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

 of an animal's brain are assumed by the remaining 

 portion. L., Wallerian, of Degeneration ; bom 

 experiments Waller showed that the trophic centers of 

 the ventral roots of spinal nerves lie in the multipo- 

 lar 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 [law-so'-ne-ah). See Henna. 



Lax [Inks) tlaxus, loose]. Loose ; not tense. 



Laxarthrus [laks-ar f -thrus) [/axus, loose; apdpov, 

 joint]. Luxation of a joint. 



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

 Aperient ; mildly cathartic. 2. An agent that loosens 

 the bowels ; a mild purgative. 



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



loosens or relaxes. A name applied to various mus- 

 cles. L. tympani. See M. of. 



Laxitas [laks'-it-as] [L.]. I L. alvi, diar- 



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

 tinorum, diarrhea. L. ventriculi, atony of the 

 stomach. 



Laxity (Inks' ■//-<■) [laxitas, looseness]. Lack or loss 

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

 a ti- 



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

 form, or nearly uniform, thickness, -pread over or 

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

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

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

 man's. See Lamina, Bowman'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 layer-, 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 /.., 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 witli tin formation of bone. L., Papillary f 

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

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

 mentary 1 1'/* 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'-er-ing) [ME., leyer, a layer]. The 

 propagation of plants by layers. 



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

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



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

 ber of the laity. 



Lazar (/a'-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-et'-o) [Itab, a pest-house]. A quar- 

 antine establishment. Also, a place for fumigation 

 and disinfection. 



Lazari malum [laz'-ar-i ma f -luni) [L., "Lazarus' 

 ill'']. Synonym of Leprosv. 



Lazulite (laz'-u-lit) [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 

 chemistry, removing by percolation. 



Lead [led) [ME., Iced, 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, Wei r M itch el Is term 

 for the marked resistance encountered in attempting to 

 flex the legs in cases of spa-tic 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 



