Aplanatic Lens

( Optics.) A lens which causes all the rays of light which fall upon it to converge to a single point or true focus. Such a lens must be of the form nece ary to prevent aberration of light, and must also be formed of different transparent media, so as to be achromatic. These conditions cannot be perfectly obtained in actual practice. Apomorphia, (áp-o-mor'fe- ah .) [From Gr. apo , from, and morphia ,] n. ( Chem .) An organic base discovered by Dr. Matt hies sen and Mr. Wright. It is prepared by the action of hydrochloric acid on morphia at a high temperature. The physiological effects of A. are those of a non-irritant emetic and powerful anti-stimulant, the action, however, rapidly pa ing off, leaving no after ill effects. Form. C7H17NO2. According to Dr. Gee, A. always produces favorable effects when employed, and by a single dose. As the salt is free from any alcoholic irritant preparation, it can be used hypodermically. A very small dose is one-fifth of a grain by the mouth, or one-tenth by hypodermic injection (which answers the purpose much more rapidly and freely). A post axis, (a- pos'taks -is.) [Gr., from apostazo , I distil from.] ( Bot . ) Unusual discharge of the juices of plants. This may arise merely from an extreme abundance of fluid, which is in consequence discharged, as in Indian shot or the vine, from the point, or serrated top of the leaves. If, however, it is elaborated sap which flows out, either from injury or weakne of the ti ues, the effect may be injurious. And this is exactly the case in what is called gumming ; a condition which may be induced artificially, by allowing water to drop constantly over a branch. This always proceeds from injured or diseased ti ues, and is with difficulty arrested when once set up, and, if so, is the certain forerunner of fatal canker. In some cases, as in the tragacanth plant, the gum is organized, and is derived apparently from the medullary rays. In conifers, a flow of resin is often attended with the same fatal results as gumming in plums and other allied plants. In this case it seems to arise generally from root-confinement and a consequent check of circulation. Aplysi'idæ, n . pl. (Conch.) A family of slug-like gastropods, with epipodia recurved on the back, forming two ear-like lobes, and with an internal lamellar shell; the sea-hares. Appendicitis, ( i '- tis , or -el-tis) n. [From Lat. ap pendix; suff. it is , inflammation.] ( Pathol .) Inflammation of the vermiform appendix ( q . v . ) of the cæcum. -This term, which came suddenly into general use about 1894-5, is a specialization of those inflammatory abdominal disorders formerly generalized as typhlitis and perityphlitis. Causes . The causes of A. are various, exposure to cold or dampne , or some indiscretion in diet, being the most usual. It was popularly believed, at first, that A. was caused by the lodging of some small foreign body, as a grape-seed, in the appendix. This supposition has been effectively disproved by careful clinical observations. In some 3,000 consecutive surgical cases, of which a careful record was kept at a leading Western hospital during 1895-96, le than 5 per cent. proved to be complicated with grape seeds or similar small objects, and in no case were these thought to be the prime cause of the trouble. The original inflammation is almost always of a catarrhal type; but in many cases foreign substances, especially fæcal concretions, seem to be active factors in the development of the disease when a catarrhal condition of the mucous membrane already exists. In the absence of such condition, foreign bodies may be present and cause little or no disturbance; but should the membrane become inflamed, they add to the irritation by occluding the lumen of the appendix, thus favoring pus formation, ulceration of the walls, perforation, or even gangrene of the whole organ. Several forms of A. are now recognized, as acute, chronic, and recurrent; also rheumatic A. , which is observed in cases presenting a rheumatic or gouty diathesis. Acute, severe attacks occur when the bacillus communis col i is present in a virulent form; with alternate lance-shaped stalked leaves, furnishes an odoriferous wood, called Aloes-wood, or Eagle-wood, supposed to be the aloes-wood of Scripture. The wood contains an abundance of resin, and an e ential oil, which is separated, and highly esteemed as a perfume. The Orientals burn it in their temples for the sake of its slight fragrance, on which account also it was used in the palace of Napoleon I. It has been prescribed in rheumatic affections in Europe. tion or other foreign body causing pre ure, the danger rapidly increases, and, in the absence of prompt relief, death may speedily ensue. Chronic A. is marked by a constantly inflamed condition of the appendix and its immediate surroundings, causing more or le distre and some intestinal irregularities. It may continue, in various degrees of intensity, for an indefinite time; or, owing to the irritation caused by a cold, the pre ure of an unemptied cæcum, ., may swiftly develop into the acute form. Recurrent A. is that form in which attacks of moderate severity occur at intervals, with intervening periods of comparative (or entire) freedom from recognizable intestinal lesion. Symptoms. The onset of acute A. and of the periodical attacks of recurrent A. , is marked by intense cramp-like pains in the abdomen. These pains are not always located, at first, in the right iliac fo a, but may be in the left side or the upper central abdominal region; eventually, however, the pain becomes localized directly over the inflamed organ, which may generally be felt by deep palpatio... Extreme local tenderne at this spot is a valuable diagnostic sign, distinguishing A. from general peritonitis. In most cases there is vomiting, but not always nausea; the abdominal walls are rigid, especially on the right side and before the pain is localized; constipation is almost always present, but occasionally there is diarrhœa. Other common symptoms are intense thirst, a disposition to flex the thighs upon the abdomen, and the absence of abdominal respiration. In moderately severe cases, pulse-rate and temperature are not seriously affected, but a sudden fall in temperature often indicate perforation, and is therefore a suspicious symptom.-Treatment. Medical treatment, directed to the cleansing of the cæcum and large intestine, with local and general methods of allaying the inflammation, very frequently results in speedy cure, if begun in time. This plan of relief is growing in favor, as a result of experience, although some practitioners recommend excision of the appendix as the only positive cure and also as a preventive. This operation, which is effected by means of an incision about 11⁄2 inches long, is now performed with great succe by antiseptic methods, the rate of mortality being only 2 or 3 per cent., exclusive of cases in which surgical interference is made during an acute attack, or as a last resort, when the mortality is much greater-perhaps 15 to 20 per cent. It is held by some that, inasmuch as the vermiform appendix is thought to be an almost functionle organ in man, its removal is eminently desirable as a guard against po ible disease, whether it has ever shown signs of inflammation or not; but this view is not generally endorsed, nor could such an operation be advisable in every case, since complete natural obliteration of the lumen of the appendix has been frequently observed, resulting in a spontaneous cure and a condition of presumably permanent immunity from attack. See VERMIFORM APPENDIX.