1086 



THORAX. 



TABLE II. Number of Respirations, of 255 

 Phthisical Patients, per Minute (sitting). 



A sudden change in atmospheric pressure 

 affects the number of breathing movements 

 in a given time. We found the following 

 limited but sudden increase of atmospheric 

 pressure increase them as follows. In South- 

 Hetton coal-mine in the county of Durham, 

 Depth of the mine 1488 feet. 



Bavom. Thermom. 



At the level of the sea 28'72 - - 39 



At the bottom of the mine 30-26 - - 49 



Difference 



1-54 



10 C 



The additional pressure of the ^ of an 

 atmosphere increased the ordinary breathing 

 from one to three times per minute. 



This difference was purely the effect of 

 pressure, and not that of fatigue or mental 

 emotion. It might only be temporary. 

 Aeronauts inform us that diminished pres- 



TABLE KK. Effect of increased Atmospheric 

 Pressure on the "ordinary" Respirations upon 

 six healthy men. 



sure increases the number of respirations ; 

 but with them there is this difference, that 

 with diminished pressure there is a sensation 

 of a want of air. When the barometer is low 

 we feel lassitude, and call the " day heavy," 

 when in truth the air is lighter, and we ourselves 

 are heavier ; -when the barometer is high, we 

 o-enerally experience an indescribable sensation 



of pleasure the vital energies seem doubled. 

 With a sudden and considerable fall of the 

 barometer there is a transient plethora. The 

 blood-vessels become distended, owing to 

 which, together with certain hygrometric 

 changes in the air, we feel listless, and the 

 least exertion produces perspiration. Du- 

 hamel observed that, in the month of De- 

 cember, 1747, the barometer in less than two 

 clays fell 1^ in., producing a change of pressure 

 on the body of a man, of 1400 Ibs. ; this he ob- 

 serves was accompanied with many sudden 

 deaths. It is evident that with an increased 

 pressure we get more air into the lungs with a 

 given mobility; for, cceteris paribus, air, with the 

 barometer at 30 in. must be more dense than 

 the same air with the barometer at 29 in. In 

 the mine in question, we experienced a sensa- 

 tion of lightness and vigour. The number of 

 respirations are always increased when there 

 is a preternatural increase in the temperature 

 of the body. 



OF THE SOUNDS OF RESPIRATION. The 

 breaking up of the air into minute streams was 

 discovered by Laennec to produce certain 

 sounds, named "breathing sounds:" which 

 sounds are now made available in detecting 

 organic disease in the lungs. As the air 

 penetrates the lungs, it is divided and sub- 

 divided until it enters the minute air vesi- 

 cles. The air passes, 1st, through the trachea, 

 producing " tracheal sounds," a hollow 

 rough blowing ; 2nd, through the next divi- 

 sion of vessels (bronchial), producing " bron- 

 chial sounds," less hollow and termed " whiff- 

 ing or tubular ;" and, 3rd, into the air vesicles, 

 producing " vesicular sound," a soft, silky 

 murmur like a gentle breeze among the 

 leaves of trees. Dr. Jackson discovered that 

 which Laennec overlooked : this murmur 

 is not heard in expiration, while the other 

 two sounds are. Hence the expiratory 

 murmur is a morbid sign, and if heard on 

 the left side below the acromial end of the 

 clavicle, is a sure sign of some altered 

 condition of the air tubes, not compatible 

 with a healthy lung. This expiratory mur- 

 mur may sometimes be heard faintly on the 

 right side, and not be a morbid sound ; but if 

 strongly heard there, it is a morbid sign. A 

 question now arises : Why is there a murmur- 

 ing sound with inspiration and not with expira- 

 tion ? First, let us inquire what is the dif- 

 ference between the inspiratory and the 

 expiratory act ? They differ in two ways : 



1st. In Inspiration the lungs are passive ; 

 the chest threatens a vacuum, and the air 

 enters a rarefied space. In Expiration the 

 lungs are active ; there is no rarefied space ; 

 the air is squeezed out into the atmosphere. 

 This does not affect our question. 



2diy. In Inspiration a volume of air is 

 broken up into smaller and smaller streams. 

 In Expiration these small streams are collected 

 up into the original volume by larger and 

 larger streams. This answers the question. 



The hollow blowing sound in the trachea is 

 caused by the friction of the air against the 

 sides of the tube. The relation of the friction 



