ON RESPIRATION. 



place for the maintenance of life. This is frequently observed in the case of 

 penetrating wounds of the thorax, in the surgical treatment of which it is of 

 great importance to close the aperture as completely as possible ; when this 

 has been accomplished, the air that had found its way into the cavity is soon 

 absorbed, and the lung resumes its full play. Where one lung is obstructed 

 by tubercular deposit, or is prevented in any other way from rightly dis- 

 charging its function, an opening that freely admits air into the pleural cavity 

 of the other side, is necessarily attended with an immediately fatal result ; an'd 

 in this manner it not unfrequently happens, that chronic pulmonary diseases 

 suddenly terminate in Asphyxia, a communication being opened by ulcera- 

 tion, between a bronchial tube and the cavity of the thorax. 



530. The dilatation of the -chest during Inspiration, is chiefly accomplished 

 by the contraction of the Diaphragm, which, from the high arch that it pre- 

 viously formed, becomes nearly plane ; in this change of figure, it presses on 

 the abdominal viscera, so as to cause them to protrude, which they are enabled 

 to do by the relaxation of the abdominal muscles. In ordinary tranquil 

 breathing, the action of the diaphragm is alone nearly sufficient to produce 

 the necessary exchange of air ; but, when a full inspiration is required, the 

 cavity of the chest is dilated laterally, as well as inferiorly. This is accom- 

 plished by the Intercostal muscles, the Scaleni, Serrati, and others ; which, by 

 elevating the ribs, bring them and their cartilages more nearly into the same 

 direction, and thus separate them more widely from the median line. Expi- 

 ration is chiefly effected by the contraction of the abdominal muscles, which at 

 the same time force up the diaphragm by their pressure on the viscera, and 

 depress the ribs ; in the latter movement they are aided by the Longissimus 

 Dorsi, Sacrolumbalis, &c., and also by the elasticity of the cartilages of the 

 ribs, with that of the air-cells and air-tubes themselves. It is difficult to form 

 an estimate, by observations on one's self, of the usual number and degree of 

 the respiratory movements; since the direction of the attention to them is 

 certain to increase their frequency and amount. In general it may be stated 

 that from 14 to 18 alternations usually occur in a minute ; of these, the ordi- 

 nary inspirations involve but little movement of the thorax; but a greater 

 exertion is made at about every fifth recurrence. The average numerical 

 proportion of the respiratory movements, to the pulsations of the heart, is 

 about 1 to 5 or 4 ; and when this proportion is widely departed from, there 

 is reason to suspect some obstruction to the aeration of the blood, or some 

 disorder of the nervous system. Thus in Pneumonia, in which a greater or 

 less amount of the lung is unfit for its office, the number of respirations in- 

 creases in a more rapid proportion than the acceleration of the pulse ; so that 

 the ratio becomes as 1 to 3, or even 1 to 2, in accordance with the degree of 

 engorgement.* In Hysterical patients, however, a similar increase, or even a 

 greater one, may take place without any serious cause ; thus Dr. Elliotsont 

 mentions a case, in which the respiratory movements of a young female, 

 through nervous affection, were 98 or even 106, whilst the pulse was 104. 

 On the other hand, the respirations in certain typhoid conditions and in nar- 

 cotic poisoning become abnormally slow, owing to the torpid condition of the 

 nervous centres, the proportion being 1 to 6, or even 1 to 8; and in such 

 cases, the lungs not unfrequently become oedematous, from the cause formerly 

 mentioned (231 and 232). 



531. The amount, also, of the Respiratory Movements is affected by various 

 morbid conditions ; thus when dislocation of the spine takes place above the 



* See a paper by Dr. Hooker, on the Relation between the Respiratory and Circulating 

 Functions, in the Boston (N. E.) Medical and SurgicalJournal; an abstract of which will 

 be found in the British and Foreign Medical Review, vol. vi. p. 263. 



f Physiology, p. 215, note. 



