Page:The New International Encyclopædia 1st ed. v. 17.djvu/74

* RESPIRATION. 58 RESPIRATION. cause of tliis dill'crence in the sexes jirobablv lying in the narrower waist of the female requiring a compensation in the iipix;r part of the chest. There are three varieties of ordinary respiration — viz.: (1) Abdominal, or that chiclly elleetcd by the diaphragm, and seen in the motion of the ■valls of the belly; (2) eosto-inferior, or tluit in which the seven lower ribs are observed to act; and (3) costo-siipcrior, or that effected in a con- siderable degree by the upper ribs. The first va- riety occurs in infants up to the end of the third year: the second in boys after the age of three, and in men; and the third in adult females. The following points in connection with the re- spiratory movements require notice. Every com- plete act of respiration is divisible into four parts — viz.: (1) Inspiration; (2) a short pause, not always observed ; (3) expiration; and (4) a con- siderable pause, occupying, according to Vierordt, about one-iifth of the whole time required for one complete respiratory act. The act of expiration is always more prolonged than that of inspiration, the former being to the latter in the ratio of 12: 10 in adult males, and as 14: 10 in children, women, and aged persons. The numljer of respi- ratory acts performed in a minite varies at dif- ferent ages. According to Quetelet, at birth there are 44 respirations in one minute ; at 5 years of age, 26; from 15 to 20, 20; from 20 to 25, 18.7; from 25 to 30, 16: from 30 to 50, 18.1; so that from 16 to 20 may be taken as the ordinary range for healthy adults, although Hutchinson gives the wide range of from 16 to 40. The average ratio ■which the number of respirations bear to the number of pulsations in a given time is about 1: 41-,. and if there is any great deviation from this ratio, there is probably some obstruction to the aeration of the blood, or some disorder of the nervous system. Thus, in pneumonia (or inflam- mation of the lungs), in which a greater or less amount of pulmonary tissue is unfitted for its office, the number of the respirations increases in a more rapid proportion than the number of pul- sations, so that the ratio becomes as 1 : 3, or even as 1:2. In hysteria a similar or even greater deviation from the normal ratio may occur ; and Elliotson records a case in which the respiratory movements were 98, or even 106, while tlie pulse was 104. On the other hand, in certain typhoid con- ditions, and in narcotic poisoning, the respiratory acts are diminished in nimiber. the ratio of res- piration to pulsations being as 1 : 6, or even 1 : 8. When the lungs have been emptied as much as possible of air by the most powerful expiratory effort, they still contain a quantity over which we have no control, and which may be estimated at about 100 cubic inches.' To this portion of the contents of the lungs the term rcsidiuil air is ap- plied. In addition to this residual air, physiolo- gists distinguish, in connection with the respira- tory process, reserve air, which is that portion which remains in the chest after an ordinary gentle expiration, but which may be displaced at will; brenthing or iidal air, which is the volume that is displaced by the constant gentle inspira- tion and expiration; and complcmental air, or the quantity which can be inhaled by the deepest possible inspiration, over and above that which is introduced in ordinary breathing. The great- est volume of air that can be expelled by the most powerful expiration, which is obviously the sum of the reserve, breathing, and coinpleruental air, is designated as the vital ctipacity — a term orig- inally introduced by Ur. Hutchinson, the in- ventor of the spirometer, who found, from uearly 5000 observations, that of all the elements or factors which might be supposed to influence it, height alone stood in a definite and constant rela- tion to it, this relation being expressed by the rule that "for every inch of stature from 5 to feet, 8 additional cubic inches of air (at 60° F. ) are given out by a forced expiration after a full inspiration." Hutchinson found that 225 cubic inches is the average capacity of a healthy adult 5 feet and 7 inches tall. With regard to bodily weight as a factor, Hutchinson found that ■'when the man exceeds the average weight (at each height) b.y 7 per cent., the vital capacity decreases 1 cubic inch per pound for the next 35 pounds above his weight." Age and muscular development do not influence the result so much as might have been expected. It has been not unfrequently observed that the vital capacity is small in athletic men, and that it has been in excess in persons by no means remarkable for physical power. The maximum vital capacity met with by Hutchinson was 404 cubic inches ; this was in a man 7 feet high, whose weight was 308 poimds; the minimum was 46 cubic inches, and occurred in the case of a dwarf whose height was only 29 inches and who weighed 40 pounds. The average inspiration in a healthy man at rest is about 30 cubic inches, and this increases with exercise of any kind. When we consider that the amount of air taken in at each respiration is only about one-seventh the capacity of the lujigs, we see how slowly the air is renewed ; but the law of the diffusion of gases (q.v. ) here comes in play, for the air in the air celis and finer tubes being charged by the respiratory process with a great excess of carbonic acid, as compared with the inspired air contained in the larger tubes, a diffusion of the carbonic acid •necessarily takes place in the outward direction, while the oxygen from the air, or the air itself, similarly diffuses itself in an opjjosite direction, toward and into the air cells them.selves. The total amount of air which passes through the lungs in 24 hours must obviously vary with the extent and fre- quency of the respiratory movements. Tlie total daily amount for a person at rest is 680,000 cubic inches. This quantity is largely increased by exertion. The alterations in the inspired air effected by respiration consist essentially in the removal of a portion of the oxygen, and its replacement by a nearly corresponding bulk of carbonic acid. The amount of carbonic acid in the expired air vaj'ies inversely with the number of respirations; it reaches 5.5 per cent, (or more) when the res- pirations are only 6 in the minute, while it falls as low as about 2.6 per cent, when the respira- tions are 96 in the minute. About 4.35 per cent, of carbonic acid is, on an average, added to the air in ordinary respiration, while about 4.782 jier cent, of oxygen is removed, the actual diminution of bulk of the expired air (after the removal of the moisture obtained from the lungs) being about one forty-fifth of its volume. Hence, unless where there is free ventilation, the air in an apartment containing men or animals must soon become vitiated by containing a great excess of carbonic acid (for ordinary atmospheric air only contains about one part of carbonic acid in 2500 parts),