OF THE RESPIRATORY MOVEMENTS. 513 



The expiratory power may be augmented by the habitual performance of move- 

 ments in which they participate ; and thus the inspiratory power is the prefer- 

 able test of the vis vitse. This has been found by Dr. Hutchinson to bear some 

 relation to height, being greatest (on an average of a considerable number of 

 cases) when the stature is 5 feet 7 or 8 inches ; and diminishing above that 

 height, as well as below it. 



546. It is impossible to form a correct estimate, by observations on one's self, 

 of the usual number and degree of the respiratory movements, since the direc- 

 tion of the attention to them is certain to increase their frequency and amount. 

 In general it may be stated, that from 16 to 20 alternations usually occur in a 

 minute ;* of these, the ordinary 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 : 5, 1 : 4$, or 1 : 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 respi- 

 rations increases 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 de- 

 gree of engorgement. 2 In Hysterical patients, however, a similar increase, or 

 even a greater one, may take place without any serious cause ; thus Dr. Elliot- 

 son 3 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 narcotic 

 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 cedematous, from a cause hereafter to be men- 

 tioned ( 556). 



547. Not only the rate of the Respiratory movements, but also their extent, 

 is affected by various morbid conditions; thus when dislocation of the spine 

 takes place above the 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 adhesions between the pleural surfaces, which offer a still more direct im- 

 pediment. 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 inter- 

 fered with ; but if one side only be affected, its movements will be diminished, 

 whilst those of the other remain natural ; and the physician hence frequently 

 derives an indication 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 pre- 

 vented, 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 rheu- 



1 See Dr. Hutchinson's Table, in "Cyclop, of Anat. and Phys.," vol. iv. p. 1085. 



2 See a Paper by Dr. Hooker, on the "Relation between the Respiratory and Circulat- 

 ing Functions," in the "Boston (N. E.) Medical and Surgical Journal;" an abstract of 

 which will be found in the " British and Foreign Medical Review," vol. iv. p. 263. 



3 "Physiology," p. 215, note. 



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