Page:The New International Encyclopædia 1st ed. v. 11.djvu/870

* LARVA. 786 LARYNGITIS. which are functionally useful to the larva at some stage in its transformations. lu order to allow eveiy oryan in its develop- ment to repeat even in an abbreviated way its phylogenctie history, there is a tendency to put off the differentiation of the tissues into their definitive organs as long as ])ossible. Thus when an organ is hatched certain organs are as yet ■wholly undifferentiated, while certain others, such as muscles and nerves, are histologically dilFerentiated. The shorter the larval period the earlier certain organs must appear, and this fact sometimes necessitates their develo])ment out of their phylogenetic order, and hence obscures the ancestral history, ilaiiy of the secondary modi- tications which arc produced in larviv are for the purpose of adapting the larvie to escape from their enemies; such are transparency, jirotective coloration, or nettling organs, and many of the spinous processes on larval crustaceans and fishes. Most of the marine larvie are free-swim- ming, and are well provided with organs of locomotion for the purpose of scattering the larvic over a wide region and thus preventing undue crowding of the adults by enlarging their area of distribution. Larval stages exist in the development of cer- tain siwcies in all the groups from Infusoria up to Amphibia. A number (?f these larv;e ililfer so much in form and habitat from the adult that their nature was often unsuspecte<l by earlier observers, and they were given generic and spc- cilie names. This is the case with the zoea- of crabs, the alima. erichthus, and siiuillcrichthus of the Squilla. the pilidium of ccrtiiin ncnier- tinea (q.v.) (at first named Pilidium grans), the scolex of the ta])evorm, and the axolotl stage of the Amblystoma. 8omc of the larval forms, such as those of diplopod myriapods. crustaceans, and chordates, have few or no aflinities to other than their own groups. There are a goodly num- ber of larv;r, such as the cercaria of trematodes, aboiit which we cannot make statements as yet, and there are a great many larvic that possess aflinities with two or more groups. These stages or aflinities we consider to be the representatives of a common ancestry. Thus the planula. with its simple double-layered and bilateral structure, is probably the ancestral form of the Olente- rata. The common ancestor of the vertebrates seems to have been a hydra-like organism, double- layered, and with a central digestive cavity and with only one opening. In the ontogenetic de- velopment of vertebrates this stage is represented by the gastrula. The larvjc of insects, to which at first the term alone referred, differ very much in the degree of their development, depending on the onlcr to which they belong. Some are almost like the adult, except for the lack of wings, as in the ease of the Orthoptera, and others are legless larvfe depending entirely for food on the provi- sion made for them by their parent. The larvae of beetles we call 'grubs.' those of files 'maggots,' and of butterflies and moths 'caterpillars.' In general, the larv'se of insects may be divided into two types, the campodcaform of Brauer and the eruciform of Packard, the latter being applied to the more or less worm-like, secondary larv.'C, such as caterpillars and the maggots of flies, and of ants, wasps, and bees. The eampodea - form lana is so called from its resemblance to the stem-form of insects, eampodea; such are the nymphs of the white ant, dragon-fly, ephemera, etc. Active and voracious larva; store uji little reserve material; but the forms that pupatu, such as the grubs, maggots, and caterpillars, store up a large amount of fat. The larval forms of certain species of flies are capable of reproduc- ing their kind before they have reached maturity in all other respects. See Parthenogenesis, paragraph J'adoyLiicsis. BiBLiouiiAiMiv. Balfour, Comiitirulivc Embry- ology (Umdon. 1880-81); Fritz Miiller, Facts for Dariiin (Londim, 1809) ; Packard, TcxtUook of Entomoloipj (New York, 1898); with the writings of .(. Miiller, Brauer, C'laus, De Geer, Dohrn. Rt^auniur, Lyonnet, Faxon. Brooks, Hiley, Hyatt. .7. . Tliomi)son, and others. LARViE. ^V term used by Romans orig- inally of the souls of those who died stained with crime, and so contrasted with the Lares; then of ghosts in general. The hirvie were rep- resented in various hideous forms, or as skele- tons, in which shape they appeared in the Atellan:e. LARVIK, liir'vfk. A seaport of Norway. See Laurvui. LARYNGITIS (Neo-Lat., from Gk. X(ipu7{, laryiijc, larynx), or Inflammation of the Laky.nx. The usual catarrhal form may be either an acute or a chronic afl'ectinn. Acute laryngitis, in its more .severe form, commences with a chill, which is followed by fever, with a strong pulse, a hot skin, and a flushed face. There are also soreness of the throat, hoarseness of the voice, great difficulty in swallowing, and a feeling of extreme constriction of the larynx. There is a painful stridulmis cough, but only a little mucus is ciectc<l. tireat difllculty of breathing soon comes on. the act of insjiiration being ]]rolongcd. with wheezing, in consequence of the swollen membrane of the glottis impeding the entrance of air. On examining the fauces, the epiglottis (sec L.rynx) is observed to be of a bright red color, erect, and so much swollen as not to be able to descend and close the glottis during deg- lutition. After an hour or two the sj-mptoms subside and the patient falls asleep, breathing noisily. Tlu' trouble may recur during the night. In the morning the patient awakes apparently well, except for a cough. In very rare cases death results, after cya- nosis of the face, drowsiness, delirium, and feeble, rapid pulse. In most cases the patient suffers every night until the disease disappears at the end of four or five days. The cause of acute laryngitis is exposure to cold, inhalation of dust or irritating gases, or swallowing corrosive liquids. Ipecacuanha, tartar emetic, and a little alcoholic stimulant afford quick relief in most cases. If suffocation appears imminent, intuba- tion or tracheotomy must be employed. A cold pack to the throat, inhalations of warm steam, or of steam inqiregnated with compound tincture of benzoin, as well as internal administration of the bromides, give relief. Chronic lar igitis oc- curs in public speakers or singers from over-use of the vocal cords (generally in neurotics), as well as in millers, masons, and others who ha- bitually inhale dust. Local applications of ni- trate of silver and other astringents, as also change of climate, improve these cases. An- other form is tubercular laryngitis; this occurs usually as a complication of pulmonary tubercu-