Page:The New International Encyclopædia 1st ed. v. 17.djvu/73

RESORCIN. agreeable pungent aftcr-tiiste. It is freely sol- uble in water, alcobol, etber, benzene, amyl al- cohol, giyeerin, and otlier organic liquids. Re- sorcin is largely used in the arts for the prepara- tion of phthalein dyes, such as Huoreseein, eosin, etc.; it is also employed in the nuinufaeture of azo-colors. It is often used in medicine. Wlicn applied externLilly it has the effect of removing scales in elironic skin diseases; it is an excel- lent remedy for dandruff, a mi.xture of resorcin and glycerin being best emjiloyed for this pur- pose. Administered internally, in dilute form, it is very valuable in fermentative dyspepsia. RESPIRATION (Lat. rcspiratio, from respi- rare, to breathe), Oroans and Process of. The two great objects of respiration are: (1) To supply that amount of oxygen to the body which is essential to its economy, and (2) to re- move the carbon dioxide which has been pro- duced as a waste ]iroduct. We may consider the anatomical details of the respiratory process in man and mammals under three different heads. First, there must be a special respiratory organ — the lungs — affording by its internal arrange- ment an immense extent of internal surface, cov- ered by vascular network, through which the blood flows in innumerable minute streamlets, onlj' separated by an extremely thin membrane from the atmospheric air that has been inhaled : secondly, there must be such an arrangement of the circulating system that fresh blood may be continually driven through the lungs, and then onward to" the general system : and thirdly, there must lie arrangements for the frequent and regu- lar change of air contained in the lungs. The special organs of respiration consist of the larynx, the trachea, the«bronchi. and the lungs. For a description of tlie first two, see Larynx; Trachea. The two bronchi resemble the trachea in struc- ture except that the incomplete rings are distrib- uted on all sides of the tubes. The bronchi on entering the lungs divide into smaller and smaller branches until finally each minute branch termi- nates in a puhnonary lohiilr. The xmnVcr bronchi, as they are called, lose their cartilaginous rings and the circular or transverse muscular layer forms a distinct coat. The mucous membrane is very delicate and lined with ciliated epithe- lium. Within the lobules of the lung the smaller bronchi divide still further into more minute branches and their structure becomes more deli- cate, iintil at last they consist only of a thin membrane lined l)y a single layer of squamous epithelium. At this point they widen out into small funnel-like air spaces (intcrceUulur pas- sages), the walls of which bulge irregularly in different places into small sac-like dilatations which are the air ccUa of the lungs. These air cells are from ^^th to jjTjth of an inch in diam- eter. Tlieir walls are very thin and are lined by a single layer of flattened cells continuous with those of the intercellular passage. The air vesi- cles of one lobule do not communicate with those of another, nor even with those of adjacent inter- cellular passages as a rule. Therefore any ob- struction of a bronchus cuts off the supply of air to the lobule beyond. Elastic tissue fills in the space between the air cells and within this elastic tissue ramifies a dense network of capillary blood vessels %vhich lies close against the air cells and which is separated from their contents by only 57 RESPIRATION. an extremely delicate membrane. It is here that the interchange of gaseous elements between the atmosphere and llie blood takes place. The pulmonary lobules are bound together by connective and clastic tissue to form very nuicli larger structiucs calle<l lubes. Of tlu'se lobes the right lung presents ibree and the left two. Kaeh lung is enveloped by a serous covering Ihi- phit- ru — which is relleded from the lung at the point where the bronchus and great blood vessels enter and passing outward line the cavity of the chest. (.See Pleira.) In health there is no space lie- tween the layer of the pleura which covers the lung and that which lines the chest wall, but in disease or injury serum, blood, pus, or air may collect therein. These conditions are termed re- spectively plcurift)/ H-itIi cffi/vio/i, huniiito-lhorax, pi/o-lhonix or emjiyenta, and pncumollwrux. In consequence of the great number of air cells which constitute their substance (over liOO,- 00(1.000. it has been calculated), the lungs (except in tlie f(etal state, when no air enters them) are the lightest organs, in relation to their size, in the body. Altliciugh their bulk is so great that, with the licart, tlicv occu])V almost the whole of the cavity of the chest, they only weigli aliuut three pounds and a half in men, and two pounds and three-quarters in women. Their color varies at dillercnt ages. At birth they are of a |)inkish white tint: in adult life they are of a slate color, and present a mottled appearance; and in old age they become of a still darker tint. The polygonal markings which are seen on the surface corre- spond to the outer surface of the lobules already noticed. Their shape is adapted to that of the cavity in which they are lodged, each hmg being conical in form, with its apex rising into the neck, while its base, which is broad and concave, rests upon the convex surface of the diaphragm ; and between the two lungs lie the heart and the great vessels that proceed from it. During life — except in certain diseases, as, for instance, jieri- carditis (q.v.) — the inner margins of the lung.s nearly overlap the heart, leaving only a roundish space of that organ, less than two inches in diam- eter, uncovered, while their lower borders extend to the cartilages of the ribs, and fit into the angle formed between those cartilages and the dia- phragm. For the method by which the blood is perpetu- ally changed in the lungs, see (Circulation. For a description of the shape and framework of the chest, see Chest. The chest (or thorax, as it is termed by anatomists) is so constructed as to be capable 'of enlargement in height (ver- tically), in depth (or from the front backward), and in wiilth (or from. side to side). Its height is increased mainly by the descent of the diaphragm, and to a certain extent by the elevation of the ribs and the widening of the intercostal spaces; while its depth and width are increased by the elevation of the ribs, which carry forward and elevate the breast -bone (or sternum), especially at its lowest end. and are slightly rotated on an imaginary axis, joining their extremities, by which their central portion is raised, and slightly removed from the mesial plane of the chest. It is only in forced or deep inspiration that all these means of enlarging the chest are called into pbiy. An ordinary inspiration is attended in men with very slight elevation of the ribs (aboit one-twen- tieth of an inch), while in women Ihe elevation is much greater, especially in the upper ribs, the