NATURE OF THE FUNCTION. 399 



origin of the intercostal nerves, but below that of the phrenic, so that the 

 former are paralyzed, the respiratory movement is confined to the diaphragm ; 

 and as this is insufficient, serum is effused into the lungs, and a slow Asphyxia 

 supervenes, which usually proves fatal in from three to seven days. Even 

 where the muscles and nerves are all capable of action, the full performance 

 of the inspiratory movements is prevented by the solidification or engorgement 

 of any part of the lung, which interferes with its free distension ; or by adhe- 

 sions between the pleural surfaces, which offer a still more direct impediment. 

 When these adhesions are of long standing, they are commonly stretched into 

 bands, by the continual tension to which they are subjected. If the impeding 

 cause affect both sides, the movements of both will be alike interfered with; but 

 if one side only is affected, its movements will be diminished, whilst those of 

 the other remain natural ; and the physician hence frequently derives an indi- 

 cation of great value, in regard to the degree in which the lung is incapable 

 of performing its functions. It is to be remembered, however, that the action 

 both of the diaphragm and of the elevators of the ribs may be prevented, by 

 pain either in the muscles themselves or in the parts which they move ; thus the 

 descent of the diaphragm is checked by inflammation of the abdominal viscera 

 or of the peritoneum; and that of the intercostals by rheumatism, pleuritis, 

 pericarditis, or other painful disorders of the parts forming the parietes of the 

 thorax. 



532. In regard to the capacity of the Lungs, the quantity of air introduced 

 and expelled at each ordinary respiratory movement, and the amount that 

 remains after expiration, great discrepancy exists in the statements of the vari- 

 ous experimenters who have endeavoured to ascertain them. This discrepancy 

 has doubtless arisen in part from the circumstance already mentioned, that 

 attention to the respiratory movements will render them fuller and more fre- 

 quent : and in part, also, from the degree of effort that is required, to draw air 

 from any kind of apparatus adapted to afford a measurement of the quantity 

 inhaled; which effort will of itself cause the distension of the chest to be 

 much greater than natural. The experiments of Messrs. Allen and Pepys 

 seemed to give 16 cubic inches as the average quantity taken in at each 

 inspiration : whilst those of Menzies (who is followed by Dr. Bostock) caused 

 him to rate it at 40 cubic inches. The most recent experiments on the subject 

 are those of Mr. Coathupe,* in which the Author has much reason to feel con- 

 fidence. According to his estimate, about 286 cubic feet, or 460,224 cubic 

 inches of air, pass through the lungs in 24 hours ; reckoning the average 

 number of inspirations at 16 per minute, this would give 20 cubic inches as 

 the amount inhaled at each. According to the experiments of Allen and 

 Pepys, the quantity of air remaining in the lungs of a stout full-grown man 

 after death, is about 100 cubic inches ; this is probably less than the amount 

 that remains after ordinary expiration.! 



* Athenaeum Report of Meeting of the British Association, 1839, p. 702. 



j- [ Many very interesting and practically important results have been obtained by Mr. 

 Hutchinsori,t with his spiromefer, an instrument by which the capacity of respiration is 

 measured by the quantity of air expired in a full and forcible expiration. Among these 

 the chief is the fact of the existence of an intimate relation between this capacity and 

 the height of the individual examined. In 1088 healthy men from five to more than six 

 feet in height, he found the capacities of respiration as follows: in men of 5 feet, 135 

 cubic inches; of 5 feet 1 in., 177 c. i.; of 5ft. 2 in., 173 c. in.; of 5 ft. 3 in., 184 c. i.; of 

 5 ft. 4 in., 193 c. in.; of 5 ft. 5 in., 208 c. in.; of 5 ft. 6 in., 204 c. in.; of 5 ft. 7 in., 224 

 c. i.; of 5 ft. 8 in., 220 c. i.; of 5 ft. 9 in., 229 c. i.; of 5 ft. 10 in., 246 c. i.; of 5 ft. 1 1 in., 

 254 c. i.; of 6 ft., 255 c. i.; of upwards of 6 ft., 260 c. i. These numbers are such that 

 it may be generally stated that for every additional inch of height from 5 to 6 feet, eight 

 additional cubic inches of air, at 60, are given out by a forced expiration. And the 



[* Lancet, July 27 and Aug. 3, 1844.] 



