THEORY OF RESPIRATION. 



79 



And the absorption of one volume of oxygen 

 can only cause, directly, the separation of 

 an equal body of caroonic acid. Conse- 

 quently, the substance or compound which 

 has lost its oxygen, during the passage of 

 arterial into venous blood, must have been 

 capable of absorbing or combining with car- 

 bonic acid ; and we find, in point of fact, 

 that tne living blood is never, in any state, 

 saturated with carbonic acid ; that it is capa- 

 ble of taking up an additional quantity, 

 without any apparent disturbance of the 

 function of the globules. Thus, for exam- 

 ple, after drinking effervescing wines, beer, 

 or mineral waters, more carbonic acid 

 must necessarily be expired than at other 

 times. In all cases, where the oxygen of 

 the arterial globules has been partly ex- 

 pended, otherwise than in the formation of 

 carbonic acid, the amount of this latter gas 

 expired will correspond exactly with that 

 which has been formed ; less, however, will 

 be given out after the use of fat and of still 

 wines, than after champagne. 



According to the views now developed, 

 the giobules of arterial blood, in their pas- 

 sage through the capillaries, yield oxygen 

 to certain constituents of the body. A small 

 portion of this oxygen serves to produce the 

 change of matter, and determines the sepa- 

 ration 01 living parts and their conversion 

 into lifeless compounds, as well as the form- 

 ation of tne secretions and excretions. The 

 greater part, however, of the oxygen is em- 

 ployed in converting into oxidized com- 

 pounds the newly formed substances, which 

 no longer form part of the living tissues. 



In their roturn towards the heart, the 

 globules which have lost their oxygen com- 

 bine with carbonic acid, producing venous 

 blood ; and, when they reach the lungs, an 

 exchange takes place between this carbonic 

 acid and the oxygen of the atmosphere. 



The organic compound of iron, which 

 exists in venous blood, recovers in the lungs 

 the oxygen it has lost, and, in consequence 

 of this absorption of oxygen, the carbonic 

 acid in combination with it is separated. 



All the compounds present in venous 

 blood, which have any attraction for oxygen, 

 are converted, in the lungs, like the glo- 

 bules, into more highly oxidized com- 

 pounds ; a certain amount of carbonic acid 

 is formed, of which a part always remains 

 di?olved in the serum of the blood. 



The quantity of carbonic acid dissolved, 

 or, of that combined with soda, must be 

 equal in venous and arterial blood, since 

 both have the same temperature ; but arterial 

 blood, when drawn, must, after a short time, 

 contain a larger quantity of carbonic acid 

 than venous blood, because the oxygen of 

 the globules is expended in producing that 

 compound. 



Hence, in the animal organism, two pro- 

 cesses of oxidation are going on ; one in 

 the lungs, the other in the capillaries. By 

 means of the former, in spite cf the degree 

 of cooling, and of the increased evapora- 



tion which takes place there, the constan 

 temperature of the lungs is kept up; while 

 the neat of the rest of the body is supplied 

 by the latter. 



A man, who expires daily 13-9 oz. of car- 

 bon, in the form of carbonic acid, consumes, 

 in 24 hours, 37 oz. of oxygen, which occupy 

 a space equal to 807 litres=51,648 cuoic 

 inches (Hessian.) 



If we reckon 18 respirations to a minute, 

 we have, in 24 hours, 25,920 respirations ; 

 and, consequently, in each respiration, there 

 are taken into the blood fi||=l'99 cubic 

 inch of oxygen. 



In one minute, therefore, there are added 

 to the constituents of the blood 18 X 1'99= 

 35-8 cubic inches of oxygen, which, at the 

 ordinary temperature, weigh rather less than 

 12 grains. 



If we now assume, that in one minute 10 

 Ibs. of blood pass through the lungs, (Miiller, 

 Physiologie, vol. i. p. 345,) and that this 

 quantity of blood measures 320 cubic inches, 

 then 1 cubic inch of oxygen unites with 9 

 cubic inches of blood, very nearly. 



According to the researches of Denis, 

 Richardson, and Nasse (Handworterbuch 

 der Physiologie, vol. i. p. 138,) 10,000 parts 

 of blood contain 8 parts of peroxide of iron. 

 Consequently, 76,800 grains (10 Ibs. Hes- 

 sian) of blood contain 61-54 grains of per- 

 oxide of iron in arterial blood, = 55' 14 of 

 protoxide in venous blood. 



Let us now assume that the iron of the 

 globules of venous blood is in the state of 

 protoxide. It follows, that 55*14 grains of 

 protoxide of iron, in passing through the 

 lungs, take up, in one minute, 6*40 grains 

 of oxygen (the quantity necessary to con- 

 vert it into peroxide.) But since, in the 

 same time, the 10 Ibs. of blood have taken 

 up 12 grains of oxygen, there remain 5-60 

 grains of oxygen, which combine with the 

 other constituents of the blood. 



Now, 55-14 grains of protoxide of iron 

 combine with 34-8 grains of carbonic acid, 

 which occupy the volume of 73 cubic inches. 

 It is obvious, therefore, that the amount of 

 iron present in the blood, if in the state of 

 protoxide, is sufficient to furnish the means 

 of carrying or transporting twice as much 

 carbonic acid as can possibly be formed by 

 the oxygen absorbed in the lungs. 



The hypothesis just developed rests on 

 well-known observations, and, indeed, ex- 

 plains completely the process of respiration, 

 as far as it depends on the globules of the 

 blood. It does not exclude the opinion that 

 carbonic acid may reach the lungs in other 

 ways ; that certain other constituents of the 

 blood may give rise to the formation of car- 

 bonic acid in the lungs. But all this has no 

 connexion with that vital process by which 

 the heat necessary for the support of life is 

 generated in every part of the body. Now 

 it is this alone which, for the present, can 

 be considered as the object truly worthy of 

 investigation. It is not, indeed, uninterest 

 ing to inquire, why dark blood becomes 



