RESPIRATION. 



RESPIRATION*. 



that U> capacity of respiration U not affected by weight* under 

 161 Iba, or lit stones ; but that above tbU point it U diminished at 

 the rmU of oo cubic inch for every additional pound up to UMlbs., 

 or 14 stones ; ao that, for example, whan a man of 5 feet 6 inches, 

 and weighing leu than 11 4 stones, should be able to expire 217 cubic 

 es, one of 



'the same height, weighing 124 stones, might expire only 

 90S cubic inches. 



" By age the capacity appean to be increased from about the 15th 

 to the 35th year, at the rate of five cubic inches per year ; from 35 to 

 AS it diminishes at the rate of about a cubic inch and a half per year, 

 ao that the capacity of respiration of a man 60 yean old would be 

 about SO cubic inches less than that of a man 40 yean old of the same 

 height and weight 



44 Mr. Hutchinson's observations were made almost exclusively on 

 , and his conclusions are perhaps true of them alone ; for women, 

 to Bonrgery, hare only half the capacity of breathing that 

 i of the same age have. 



"The number of respirations in a healthy adult person usually 

 ranges from 14 to 18 per minute. According to Mr. Hutchinson, the 

 force with which the iuspintory muscles are capable of acting is 

 greatest in individuals of the height of from 5 feet 1 inches to 5 feet 

 8 inches, and will elevate a column of three Inches of mercury. 

 Above this height the force decreases as the stature increases, so that 

 the average of men of 6 feet can elevate only about 24 inches of 

 mercury. The force manifested in the strongest expiratory act is, on 

 the average, one-third greater than that exercised in inspiration ; but 

 this difference U in great measure due to the power exerted by the 

 elastic reaction of the walls of the chest, and it is also much influenced 

 by the disproportionate strength which the expiratory muscles attain 

 through being called into use for other purposes than that of simple 

 expiration. The force of the inapiratory act is therefore better 

 adapted than that of the expiratory for testing the muscular strength 

 of the body. 



" Much of the force exerted in inspiration is employed in over- 

 coming the resistance offered by the elasticity of the walls of the 

 best and of the lungs. Mr. Uutchinson estimated the amount of 

 this elastic resistance by observing the elevation of a column of 

 mercury raised by the return of air forced, after death, into the lungs, 

 in quantity equal to the known capacity of respiration during life ; 

 and he calculated that in a man capable of breathing 200 cubic 

 inches of air, the muscular power expended upon the elasticity of the 

 walls of the chest, in making the deepest inspiration, would be equal 

 to the raising of at least 301 Ibs. avoirdupois. In tranquil respira- 

 tion, supposing the amount of breathing air to be 20 cubic inches, 

 the resistance of the walls of the chest would be equal to lifting more 

 than 300 Ibs. The elastic force exerted in ordinary expiration must 

 therefore be much greater than enough to lift this weight ; because 

 in it the elastic force of the longs is also in action a force which is 

 not included in tbsss estimates, because the lungs were in both cases 

 bunt by the air forced into them." (Kirkes and Paget, 'Handbook of 



The changes of the air in the lungs effected by the respiratory 

 i an assisted by the air itself. It is a well-known fact that 



carbonic add, although heavier than atmospheric air, is speedily 

 diffused through it according to the known laws of the diffusion of 

 gas**. There is no doubt that this law is in active operation during 

 the respiratory changes, and that it assists the oxygen in passing into 

 the lungs, and tha carbonic add in passing out. If it were not for 

 this interchange the reserve and residual air would probably be 

 injuriously charged with carbonic add. It is also probable that the 

 difference of temperature within and without the lungs assist in the 

 interchange of the air. 



The air which is taken into the lungs during respiration is the 

 air of tha atmosphere, which in round numbers consists of 21 of 

 oxygen, and 70 of nitrogen in every 100 part*. A small proportion of 

 carbonic acid exists in it, about 4 part* in 10,000. It also contains a 

 varying quantity of watery vapour. The change* which occur in this 

 air during respiration an 1. It contains a larger quantity of carbonic 

 add gas. 2. Its oxygen is diminished. 3. It* watery vapour is 



An easy proof of the existence of carbonic acid in the nir expired 

 from the lungs, is afforded by blowing through a tube into lime water, 

 when the carbonic add will unite with the lime, and carbonate of 

 limn will be precipitated. The quantity of this gas which is calcu- 

 lated by Valentin and Brunner, as thrown out from the lungi in 

 24 hours, is 1345-3 cubic inches, or about 636 grains an hour. This 

 would make about 173 grains of carbon in an hour, or 8 ounces in 

 the S4 hours. Andral and Qavarret calculated the quantity at 



ounce., and Mr. Coathupe at 5 ounces. Liebig gives 18 ounces as 

 the quantity of carbon thrown off from both the skin and lungs. 



The quantity of carbon however which is thrown out from the 

 longs varies under different circumstances. As is seen in the table 

 above, sex sad age make a comiderable difference in the quantity of 



Diet exercises a considerable influence on the quantity of carbon 

 thrown out from the lungs. The following toble exhibits the quantity 

 of oxygen required by certain articles of diet to convert them into 

 carbonic add and water. It should always be recollected in relation 



to this subject, that although carbon U spoken of so frequently, that 

 not only is carbon oxidated, but also hydrogen. Wherever hydrogen 

 is present in the tissues, it sustains apparently the same relation to 

 oxygen as carbon. Hence, in the calculation of the influence of diet 

 on respiration it should never be left out : 



From this table it may be gathered that vegetable diet consume* 

 more oxygen in the production of carbonic acid and water than animal 

 diet This is also found to hold good in the case of carnivorous and 

 herbivorous animals the latter taking up a larger quantity of oxygen 

 than the former, as seen in the following result of an experiment by 

 Uegnault and Heiset : 



The same result is indicated by the following experiment ou 

 Birds: 



It has been found that the carbon and hydrogen of nitrogenous 

 foods become oxidised, and are given out during respiration, but they 

 do not supply sufficient for the wonts of the system, and when animals 

 are fed on nitrogenUed foods, the fat is oxidised and converted into 

 carbonic acid and water. 



It appean to be now an established fact, that the imbibition of 

 spirituous drinks of all kinds is attended by a diminished excretion of 

 carbonic add. This was indicated by Prout, and bag since been con- 

 firmed by Vierordt and others. This shows the importance of such 

 drinks in conns where the oxidating processes are proceeding too 

 rapidly, and of their injurious tendency where these processes need 

 to he stimulated. Dr. Prout observed that strong tea exercises the 

 same influence on the system. 



Sleep produces a very considerable diminution of tho excretion of 

 carbonic acid. Scharling found that the ratio of carbonic acid exhaled 

 during sleep in one hour in the night, to that eliminated in one hour 

 in the day after dinner, was as 81'39 to 4074. A much greater differ- 

 ence U found between animals during their waking and hybernating 

 states. 



Bodily exercise increases the exhalation of carbonic acid, whilst rest 

 diminishes it Seguin, Trout, Vierordt, and Hoffman, have all proved 

 this by experiment 



