428 



SCIENCE. 



[Vol. II., No. 34. 



high altitudes than at sea-level. M}- own ex- 

 perience is, that resolution in such cases is 

 more rapid, and that the chest ' clears up ' 

 sooner. Maj' not this be explained on the 

 ground of the increased rapidit}' of circulation ? 

 We know that the clearing-up is brought about 

 by the expectoration of the morbid products of 

 the exudation, and further, and chieflj-, by 

 their absorption into the circulation. If this 

 be true of an acute trouble, is it not also appli- 

 cable to a chronic asthenic one? 



Further, the increase of rapidity in the cir- 

 culation means that the same blood is brought 

 more frequentlj' to the lungs to be oxygenated, 

 — an increase in the number of times, which 

 we have seen to be equal to 29,622 additional 

 times, per diem. This would indicate an in- 

 crease in the activity of the metamorphosis of 

 tissue, and therefore an increased vital force. 

 This is clinically perceptible in the exhilaration 

 that invalids experience on coming to higher 

 altitudes, and b}- the increase in appetite de- 

 pendent upon the demand for material to meet 

 the additional metamorphosis. 



There is the other side, however, which 

 must be alluded to. An increase in the rapid- 

 ity of the circulation means an increased flow 

 or tendency of blood to the diseased parts, in- 

 volving, as it does, a greater activity of these 

 parts. This is temporarily noticeable in every 

 case of phthisis pulmonalis coming to higher 

 altitudes, and is evidenced by an increased 

 expectoration. This, as we have said, ma}- 

 be beneficial by assisting to remove the mor- 

 bid products ; but in enfeebled cases, where 

 the ravages of the disease are great, it may be 

 highlj- injurious in assisting the already great 

 breaking-down of the tissues. Again : there 

 is an increased demand for oxygen dependent 

 on all of these causes, and, in cases where the 

 amount of lung-tissue involved is so great as 

 to cause a considerable embarrassment of the 

 respiration, this additional strain is not desir- 

 able. 



2. Effect on respiration. — We must now 

 study another effect produced upon the system 

 by an increase in elevation, and that is, the 

 effect produced upon the respiration. Here, 

 too, we shall have to speak of gross results, 

 and leave minutiae unexplained. 



Experience shows that the respirations are 

 deepened and fuller, and that they are, at first, 

 at least, increased in number. 



This can be explained somewhat in the fol- 

 lowing way. The nervous action, the effect 

 upon the respiratorj* centre, etc., is so compli- 

 cated, that, despite its importance, we shall 

 leave it without attempting its solution ; and 



we shall only attempt an explanation of the 

 quasi physical or mechanical results. 



The lungs are elastic bags suspended in a 

 closed cavitj'. During inspirations the respi- 

 ratory muscles draw the ribs upwards, enlarge 

 the cavity, and produce a partial vacuum, in 

 consequence of which the air rushes in to fill 

 up this vacuum, and the lungs are inflated. 



It is evident that in inspiration the respira- 

 tor^' muscles, in raising the chest-walls, displace 

 a certain amount of air, and overcome a cer- 

 tain resistance due to atmospheric pressure, 

 and that these muscles, accustomed to exert a 

 given amount of force to overcome this resist- 

 ance (which ma}' be roughlj' measured by the 

 diflference between the positive pressure on the 

 outside and the negative pressure on the in- 

 side of the chest-walls) , would continue to ex- 

 ert this force, even though the resistance were 

 diminished. As a result of this, we should 

 expect either a greater expansion of the chest 

 from the same expenditure of force, or an in- 

 crease in the number of inspirations. 



The beneficial results of a greater depth of 

 inspiration will be more clearly seen if we con- 

 trast it with the bad results of diminished res- 

 piration. Ruehle, in Ziemssen's Cyclopaedia, 

 saj's, — 



"The dimuiished respiration in the upper parts of 

 theluiig3, and the exaggerated respiration in the lower 

 parts resulting from this cause, serve to explain the 

 very general fact that pulmonary consumption almost 

 always begins at the apices of the lungs. But there 

 is probably another cause in the peculiar position of 

 these parts. They project from three to four centi- 

 metres above the clavicles ; and this projecting por- 

 tion, being situated outside the chest, is subjected to 

 the pressure of the external air. The supraclavicular 

 region sinks in during deep inspiration, and conse- 

 quently the inspiratory expansion of the apices is 

 less than that of other parts of the lungs." 



It is evident, if Ruehle be right, that a dimi- 

 nution of atmospheric pressure means a greater 

 expansion of the apices, due to a diminution 

 of atmospheric pressure bearing on those parts, 

 and also a greater expansion of the entire 

 chest. 



There is, however, a theorj^ often advanced, 

 that the greater depth of respiration is due to 

 the fact, that, in consequence of the diminu- 

 tion of the amount of oxygen dependent upon 

 the decreased atmospheric pressure, an indi- 

 vidual will have to breathe more frequentl}- 

 and deeper to gain the amount of oxygen neces- 

 sarj' for aerating the blood. The theor}-, it 

 seems to us, is misunderstood, and the ques- 

 tion needs investigation. 



We have shown that there is an increased 

 demand for oxygen dependent upon an in- 

 creased teudencj- of the blood to the lungs. 



