814 SPECIAL PHYSIOLOGY. 



ing respiratory act, 1. The period of motion to that of rest, is there- 

 fore as 9 to 1. (Walshe.) According to Vierordt, the period of inspi- 

 ration being equal to 10, that of expiration, together with the pause, 

 is, in deep respirations, 14 ; in quick breathing, 24. As he estimates 

 the pause at one-fifth of the whole period, the numbers representing 

 the inspiration, the expiration, and the pause, would, in the former 

 case, be 10, 9, and 5, and in the latter 10, 17, and 7. According to 

 recent observations with the sphygmograph and kymographion, the 

 whole respiration period being 15, inspiration occupies 4, expiration 2, 

 and the pause 9 parts ; the ratio of the movement to the pause is as 2 

 to 3. (Sanderson.) In the disease called emphysema, which consists 

 in a dilatation of the air-cells, the periods of expiration and inspiration 

 are equal, or the former is even longer than the latter. In cases of 

 tubercular deposit, the expiration is also prolonged. 



The force exercised by the inspiratory muscles in ordinary respira- 

 tion, in an adult man, varies from about 1.5 inch to 4.5 inches of 

 mercury ; but, in exceptional cases, it may rise to even 7 inches. 

 This force increases more rapidly than the actual amount of expan- 

 sion of the chest, for when, in the same body, 70, 90, 190, and 200 

 cubic inches of air were injected into the lungs, the pressure was 

 found to be 1, 1.5, 3.25, and 4.5 inches of mercury. The expira- 

 tory force is, on an average, about one-third or one-fourth stronger 

 than the inspiratory force, varying from 2 to 5.8 inches of mercury, 

 and rising even, in certain cases, to 10 inches. (Hutchinson.) This 

 is due to the co-operation of the elasticity of the lungs, and the 

 resilience of the chest-walls, with the muscular effort. The force of 

 the inspiration is, therefore, the severer test of the strength of the 

 body. . The expiratory power is said to be greater in men of 5 feet 7 

 or 5 feet 8 inches in height, than in those either above or below that 

 stature. 



The entrance and escape of the air into, and out of, the air-tubes 

 and air-cells, during inspiration a,nd expiration, produce certain sounds 

 named respiratory murmurs, which may be heard by the ear placed on 

 the chest or by aid of the stethoscope. In health, the inspiratory and 

 expiratory murmurs, named the bronchial or tubular sounds, which 

 depend on the movement of the air through the air-tubes, are heard 

 over the site of the larger bronchia, between the scapulae, and over 

 and near the upper part of the sternum. They are distinct, and char- 

 acterized by a soft blowing noise; those of inspiration and expiration 

 are of nearly equal duration. The vesicular respiratory murmurs, 

 dependent upon the entrance and escape of the air in, and out of, the 

 air-cells, are only faintly audible, like a gentle breezy noise; the ex- 

 piratory vesicular murmur is weaker, and three or four times shorter, 

 than the inspiratory murmur. The duration of the sounds is altered 

 by the same causes as those which modify the length of the move- 

 ments of inspiration and expiration. 



Accumulations of mucus or other secretions in the air- tubes, produce ab- 

 normal sounds, which are named rhonchi, or rales. These vary in character, 

 according to the seat, quantity, and nature of the secreted matters. Thus, a 

 line crepitant rhonchus is produced by fluid exudations in the air-cells, in pneu- 





