September 28, 1883.] 



SCIENCE. 



427 



Elevation. 



The eflect of a rise in elevation is to dimin- 

 ish the atmosplieric pressure. The method of 

 measuring this etfect is bj- means of the mer- 

 curial barometer. Disregarding the variations 

 attributable to changes in temperature, humid- 

 it}-, and latitude, it can be broadly stated that 

 the barometer will fall one inch for a rise of 

 857 feet above sea-level, two inches for a rise 

 of 1,743 feet, three inches for a rise of 2,C(11 

 feet, etc. ; or, for the purposes of a rough cal- 

 culation, it may be said that the barometric de- 

 pression is one iuch for every thousand feet of 

 elevation. This depression would indicate a 

 diminution in atmospheric pressure of one- 

 sixth in weight for an elevation of .5,000 feet; 

 or, to state this fact in another way, the atmos- 

 pheric pressure at sea -level being lo lbs. to 

 the square inch, at ;j,000 feet it would be one- 

 sixth less, or 12.V lbs. To illustrate : if the 

 pressure on the entire surface of the bodj- of 

 a man of middle size be 35,560 lbs. at sea- 

 level, at 5,000 feet it would be 29,035 lbs., a 

 diminution of nearly three tons. 



The question for u.s to consider is, what 

 cHect this diminution of pressure has upon the 

 vital functions with reference to the cure of 

 phthisis. 



1. Effect on circulation. — The heart is a 

 muscular organ, habituated to expend a certain 

 amount of force, which m.ay be rougiily esti- 

 mated as 75,000 kilogrammetres, or 542,475 

 foot-pounds, per diem. To accomplish this 



work at sea-level, the heart makes 72 Ijeats a 

 minute, or 103,080 beats a day. Allowing, 

 now, an increase of two beats a minute for 

 every thousand feet of elevation, at 5,000 feet 

 there will be an increase of 10 beats a minute, 

 or 14,400 beats a d.i}', — an increase in work 

 equal to about 74,744 foot-pounds in a day. 



This in itself would prove that such an ele- 

 vation is to be avoided in those cases where an 

 enfeebled heart is struggling to overcome the 

 dis.idvantages produced by organic lesions. 



What eflect does this increase of heart-work 

 have upon the circulation ? The rapidity of cir- 

 culation is influenced by the force and rapidity 

 of the heart's lieat, and by the diminution of 

 the peripheral resistance. At an elevation 

 of 5.000 feet, each of these causes would be 

 at work. To just what extent the}- work, 

 in producing given results, it is impossible 

 to say ; but, allowing that the peripiieral re- 

 sistance and the force of the heart's lieats 

 remain tiie same at 5,000 feet as at sea-level, 

 an increase in frequency of ten ))eats per 

 niiuute would indicate, that, on account of this 

 one factor, the blood would make 29,622 ad- 

 ditional circulations through the System per 

 diem. What effect would this have upon the 

 disease in question? 



It is a frequent remark that both waste and 

 repair are more rapid at iiigh altitudes than 

 at sea-level. Experience amongst physicians 

 show.s that cases of fibrinous pneumonia are 

 more acute and more rapid in their results at 



