Page:The New International Encyclopædia 1st ed. v. 06.djvu/670

* £AK. 582 EARL. toid is then obliterated. Drainage is secured by means of a tube passed into the bony meatus, and the external incision is closed up and a dressing applied. Consult: tirav, Aiiaiomi/, Descriptive and Sur- gical (Philadelphia, I'.tOO) : tJerrish (editor), A Text-BooU of Anulonn/ bii Aiiuricaii Authors (Philadelphia, 18!)!)): Halliburton. Ai/te's Hoiid- book of Physioloi/y (Philadelphia, 15)01) ; Deneh, Diseases of the Kur (New York, 18!)!i) ; Uacon, Manual of Otology (Xew York, 1900); Article "Ear" in Reference Handbook of the Medical Sciences (New York, inOO). See Audition; Acoustics. eab, comp.^r.vtive a>,atomy of the. the question of the licaring powers of animals is still a subject of dispute, and we cannot say positively whether the lower animals are conscious of sound- waves, as such, or not. But if we bear in mind that the human ear is not merely an organ of hearing, but is also the means by which we de- termine our position (in other words a positional organ), then we are justiticd in saying that many invertebrates have ears, even though we ticny them the sense of hearing. Positional and Chobdotonal Organs. Posi- tional organs as found in the simplest conditions are minute balls of mineral matter susjiended in a Hexible club-shaped liody. and are known as ■sense-clubs.' They are formed on the margin of the bell in many medusae. In some cases they are surrounded by long hairs against which they strike when they move. In a still more ad- vanced condition, they are situated in a depres- sion, and the surrounding tissue grows over and about them, so as to inclose them in a cavity. It is but a step from such a condition to the form of positional organs, called otocyst, which occurs in many invertebrates. An otocyst is a spherical cavity lined with cilia and containing one or more balls of mineral matter called otoliths. The otocyst is specially and fully innervated, the stimuli coming from the movements of the otolith against the cilia, accompanying changes in the position of the body. There is no evi- dence to show that such organs are capable of detecting sound-waves. Otocysts occur in medusa", many kinds of worms, numerous mol- lusks, a few echinoderms, and the higlier Crus- tacea. In the latter, the vesicles often remain open and the otolitlis are grains of sand; the vesicles are lined with delicate hairs, some of which are actually attached to the otoliths. In- sects have no otocysts, but in their place we find remarkable slruclures known as "chordotonal' organs, which lie in the integument of various parts of the body. They arc largest and most liighly developed in grasshoppers, locusts, and crickets, and two or four of them are verv' large and are known as the 'tympana.' They lie on the sides of the abdomen or on the tibiic of the fore legs. Chordotonal organs seem to be par- ticularly adapted for the detection of sound- waves, but how they can serve as positional or- gans is not clear. Primitive Ai ditory Oroans. Turning now to vertebrates, we find a general agreement with the structure of the human ear. even in fishes, although in details and proportions there is much variety. In the cyckistomes it is prob- able that there is no real sense of hearing, for the semicircular canals arc the only well-de- veloped parts of the ear, and these are believed to be specially concerned with the positional function. Whether other fishes actually hear sounds is still a disputed question. The cochlea is, in fishes, simply a small knob-like appendage of the sacculus, and shows none of the complexity of the mannnalian cochlea. In most fishes large otoliths are present in the labyrinth, and in many fishes then' is direct connection between the car and the air-bladder by means of a chain of small bones. Recent experiments (1902) by Dr. G. H. Parker of Harvard apparently demonstrate the actual recognition of sounds by some fishes, and that this recognition is dependent upon the un- injured condition of the ears and auditory nerves. In .Amphibia the cochlea is more highly developed, and this part of the ear increases in comjilexity as we pass upward through reptiles to birds and mannnals. Even in crocodiles and birds, however, there is no organ of Corti in the cochlea, and there is a single bony columella in- stead of the three auditory ossicles of mannnals. In many respects the ears of nionotremes are noticeably like those of the Crocodilia. Fishes, amphibians, and most reptiles have no outer ear, and the pinna is not found fully developed any- where except in mammals, and not always there. Bibliograpiiv : Lang, t'oniparnlire Anatomy (Xew Y'ork, 18!)t)) ; Wiederslieim. Cuntparutire Anatomy of ]'ertebrales (Xew York. lS8t!) ; Ret- zius, D((.s- flehiJrori/an der ^yirbc^thierc (Stock- holm, 1881 and 1884). EAB.COCKLES, PiBi'LEs, or Pepper-(^orn. A disease in wheat caused by a nematode worm (Tylenchns tritiei). This worm is yellowish- white, slender, tapering toward the tail, and more suddenly attenuated to a point at the head. It finds its way to the dowers; the infected grains become dark green, then black, rounded like small pepper-corns, and furrowed on the surface; the glumes spread open, and the awns become twisted; the grains are filled with a white cottony substance which consists of myriads of the nematodes. The disease has not been reported in the United States. EABL (AS. eorl, leel. earl, Dan. jarl, earl, OS., OHG. erl, man, warrior). . title of the British nobility, third in rank under the ])rinces of the blood royal, next to a manniis, and above a viscount. In. glo-Saxon times the word de- noted the primitive noble by birth of the first settlement, the nobilif: of the Old Germans, as distinguished from the ceorl, or connnon freeman. From this class the magistrates, priests, and kings were clio.sen. But with the developnient of the royal power in England, and consequently of thanehood, a nobility by service, the eorl sank one degree in the social scale, and was merged into the class of thanes. In the later Saxon period the word eorl changed its significance, being used for eat- dorman. This was an administrative officer, the chief magistrate of a shire or cluster of shires. He was originally a viceroy, the subjected king of a conquered district or one of his family, or a near kinsman of the over-king {<rlhelin(i). The office might be hereditary, but it tended to become appointive. The ealdorman was apjiointed in the general assembly of the nation, and even where the office was hereditary, the consent of king and nation was necessari'. He sat with the bishop in the folkmoot of the shire, declaring