ATTENUATION 



149 



AURA 



Attenuation {at-ten-u-a' 'shun) [attenuare, to make thin]. 

 A thinning, narrowing, or reduction of the strength 

 or size of a substance. A. of Microbes, weakening the 

 pathogenic virulence of microbes by successive cul- 

 tures and other methods, so that they may be used as a 

 vaccine to confer immunity from future attacks of the 

 disease. A., Sanderson's Method of, by passing 

 the virus through the system of another animal {e.g., 

 the guinea-pig, in anthrax), so that it becomes modified 

 in virulency. Toussaint and Chauveau have shown 

 that heat is a valuable means of attenuation ; oxygen, 

 chemical reagents, exposure to sunlight, etc., have also 

 been used. 



Atterminal [at-er'-min-al) . See Adterminal. 



Attic {aP-ik) [Atlicus, Attic]. Part of the tympanic 

 cavitv situated above the atrium. A. Disease, chronic 

 suppurative inflammation of the attic of the tympanum. 



Attitude (af-e-tud ) [aptitudo, aptitude] . See Posture. 

 A., Crucifixion, in hystero-epilepsy, a rigid state of 

 the body, the arms stretched out at right angles. A., 

 Frozen, a peculiar stiffness of the gait characteristic 

 of disease of the spinal cord, especially of amyotrophic 

 lateral sclerosis. A., Passionate, the assumption 

 of a dramatic or theatrical expression, a position 

 assumed by some hysterical patients. 



Attollens [at-ol'-enz) [attollere, to rise up] . Applied to 

 muscles raising or elevating the part, as the A. Auris, 

 a muscle raising the external ear. See Muscles, 

 Table of. 



Attraction (at-rak* -shuti) [attrahere, to draw to]. The 

 tendency of one particle of matter to approach another. 

 Affinity. As existing between celestial bodies it is 

 termed gravitation , while molecular attraction or cohe- 

 sion expresses the force aggregating molecules into 

 masses. A., Chemical, the attraction of affinity, re- 

 lates to the attraction of atoms of one element to those 

 of others, resulting in chemical compounds. A., Cap- 

 illary, the tendency of a curved surface or a tube to 

 exert traction on a liquid. A., Electrical, the ten- 

 dency of bodies toward each other when charged 

 with opposite electricities. A., Magnetic, the influ- 

 ence of a magnet upon certain metallic substances, 

 chiefly iron. 



Attrahens (aP-rah-enz) [attrahens, drawing]. Applied 

 to muscles as Attrahens aurem, a muscle Ira wing 

 the ear forward and upward. See Muscles, Table of. 

 Also applied to medicines attracting fluids to a part, 

 as stimulants, epispastics, etc. 



Attrahent (af '-rah- en <t) [attrahens, drawing]. I. 

 Drawing to ; adducent. 2. A drawing application ; 

 an epispastic or rubefacient. 



Attrition (at-rish'-un) [atterere, to rub against]. An 

 abrasion or chafing of the skin. In physics, any rub- 

 bing or friction that breaks or wears the surface. 



Attypic {at-ip'-ik) [at, to; ri'-oc, a type]. In biology, 

 possessing by acquisition or specialization the charac- 

 ters of a prototype. 



Atypic (ah-titZ-ik) [a priv. ; tvttoc, a type]. Irregular; 

 not conformable to the type. A. Fever, an inter- 

 mittent fever with irregularity of the paroxysm. 



Atypical (ah-tip'-ik-al). See' Atypic. 



Auante (awan f -te) [avavrf/ ; avaivetv, to dry]. A wast- 

 ing or atrophy. 



Auantic (aw-an f -tik) [avavruute, wasted]. Character- 

 ized by wasting ; atrophic. 



Aubernage (o-bar-nahzh') [Fr.]. A contagious disease 

 of the vine, called by the Italians the Black Disease. 

 It is doubtful whether it is due to a fungus or a bac- 

 terium. Cf. Bacterium gummis, comes, under Bac- 

 teria, Synonymatic Table of. 



Auburn System. See Ventilation. 



Auctioneers' Cramp. See Cramp. 



Audimeter (azv-dinP -et-er). See Audiometer. 



Audiometer (au>-de-om' -et-er) [audire, to hear ; uerpov 

 a measure]. An instrument for measuring the acute- 

 ness of hearing. 



Audiometric (ato-de-o-meP '-rik) [audire, to hear ; 

 fierpov, a measure]. Relating to audiometry. 



Audiometry [aio-de-om r -et-re) [audire, to hear ; uerpov, 

 a measure]. The measurement, or testing, of the 

 sense of hearing. 



Audiphone {aw* -dif-on) [audire, to hear; ouv^, a 

 sound]. An instrument for improving the power of 

 hearing by conveying sounds through the bones of 

 the head to the labyrinth. 



Audition {aw-dish' '-un) [audire, to hear] . The act of 

 hearing. A. coloree, a peculiar association between 

 the auditory and optic nerves, by which a certain 

 sound or musical note will give rise to a subjective 

 sensation of color, the same note in the same person 

 being always associated with the same color. 



Auditory lavr '-dit-o-re) [audire, to hear]. Pertaining 

 to the act or the organs of hearing. A. After-Sensa- 

 tions, the sensations of sounds continuing or occurring 

 after the cessation of the stimulus. A. Amnesia. See 

 Mind-deafness. A. Area, the cerebral center for hear- 

 ing; its location is not definitely determined. A. 

 Aura, auditory sensation preceding an attack of epi- 

 lepsy. A. Center, same as A. Area. A. Hairs, the 

 processes of the crista acustica, at present of indeter- 

 minate function. A. Meatus (external and internal), 

 the external and internal canals or openings of the ear. 

 A. Nerve, the portio mollis of the seventh pair of 

 cranial nerves. A. Ossicles, the chain of small bones 

 of the middle ear. A. Sac, the labyrinth, pit, or de- 

 pression in the epiblast on both sides of the embryo- 

 logic after-brain. When cut off from the epiblast it 

 is called the vesicle of the labyrinth, or Primary 

 Auditory Vesicle. A. Teeth. See Teeth. A. 

 Vertigo, dizziness due to pathologic conditions of 

 the ear. See Vertigo and Meniere's Disease. 



Auditus (o7o-di f -tus) [L.]. Hearing; the sense or 

 power of hearing. 



Auerbach's Ganglia. See Ganglia, Table of. 



Auerbach's Plexus. See Plexuses, Table of. 



Augment ( a-og -tnent) [augmentum, increase]. The 

 increasing stage of a fever or other acute disease. 



Augmentation [azig-men-ta'-shun) [augmentatio, an ' 

 increasing]. I. Same as Augment. 2. Increase in the 

 violence of symptoms. 



Augnathus {trwg-na' '-thus) [ai; besides ; yvdthc, the 

 jaw]. A monster with two lower jaws. See Dipro- 

 sopus. 



Aula (OTiZ-lah) [avA*/, a hall or open court]. I. The 

 common mesal cavity of the cerebrum, it being also 

 the anterior portion of the third ventricle. 2. In 

 biology, a space or cavity formed by a colony of 

 infusorians. 



Aulatela (aw-lat-P lah) [aula, a hall ; tela, a web]. 

 The roof or covering membrane of the aula. 



Aulic (aw'-lik) [a'v/.i], a hall]. Belonging or pertaining 

 to the aula. A. Recess, a triangular depression 

 between the precommissure and the two fomicolumns 

 of the brain. 



Auliplexus (a?o-le-pleks / -us) [aula, hall ; plexus, a net- 

 work]. The choroid plexus of the aula. 



Aulix (a-jZ-liks) [aulix, a furrow]. The sulcus of Monro, 

 a groove on the mesal surface of the thalamus just 

 ventrad of the medicommissure. 



Aulophyte {ai& '-lo-fit) [av7.6q , a pipe or tube ; dvrov, a 

 plant]. In biology, a symbiotic plant ; one that lives 

 within another, but not as a parasite. 



Aura (aw* -rah) [avpa, a breath]. A breath of wind; 

 a soft vapor. A sensation sometimes like a gentle 



