QJF THE FUNCTIONS OF THE LUNGS. 49 



*' 5. That air admitted into both the cavities of the chest (of a middle sired dog) si- 

 multaneously through apertures of an inch and better in length in the intercostal paces, 

 will not collapse the lungs, provided the animal is allowed unconfined the use of his re- 

 spiratory organs. 



** 6. That a sound lung never fills the bag of the pleura." 



V. Of the Effects of Suspended Respiration on the Circulation. From the experiments 

 which were made by Dr. Williams, of Liverpool, on this subject, he deduces the fol- 

 lowing corollaries : 



1. The blood is obstructed in its passage through the lungs, on suspension of respira- 

 tion, while its circulation through the other parts of the body continues. 



2. The obstruction of the blood in the lungs, on suspension of respiration, is not oc- 

 casioned by a mechanical cause. This is proved by the flow of blood through the lungs 

 being sudden! arrested, without any subsidance of this organ, while the circulation 

 was carried on vigorously through the other parts of the body, in the experiments de- 

 tailed by the author. 



3. The observation of,bloodin the lungs, on suspension of respiration, arises from the 

 deprivation of pure atmospheric air. 



4. The blood, which is found after death in the left auricle and ventricle, is the rem- 

 nant after the last systole, and the subsequent draining of the pulmonary veins. 



5. The obstruction of blood in the lungs, on suspension of respiration, is one of the 

 principal causes of the vacuity after death of the system circulating arterial blood. 



6. The immediate cause of the cessation of the action of the heart is a privation of 

 its natural stimulus, arising from the obstruction of the blood in the lungs. (JInnals of 

 PhUos. Sept. 18^3.) 



Of the changes induced on the Air and the Blood by Respiration* 

 Note W. 



1. Of the production of Carbonic Acid during Respiration. The experiments of Mr. 

 Ellis and others have led physiologists to conclude, that oxygen is not absorbed by the 

 blood in the lungs from the air, during respiration, but that the blood gives off its su- 

 perabundant carbon from the surface of the air-cells and the carbonic acid is thus form- 

 ed in the lungs themselves. 



This mode of accounting for the changes induced upon the air and upon the blood 

 during respiration, has been very generally adopted in this country, while the former 

 mode of explaining the process (that which is given in the text) has still been received, 

 with various modifications, on the Continent. 



It appears to us that the production of carbonic acid gas by the respiratory function 

 has been ascribed too exclusively to one of the above processes ; and that it has been 

 too generally viewed as altogether a chemical phenomenon. When the theory of the 

 absorption of oxygen was dismissed in favour of that which contended for the discharge 

 of carbon from the blood, either in its pure state or in that of a hydrate, no participa- 

 tion in the process, by which the carbonic acid is formed, was allowed to the previous- 

 ly received opinion : however, it still appears a matter of doubt how far either function 

 predominates ; tor we are inclined to think that both operations go on simultaneously, 

 and that, whilst a portion of the carbonic acid gas is given out from the, blood, already 

 formed, it is accompanied with another portion of free carbon, or an oxide of carbon, 

 or even with an hydrate ot the same sui -stance which combines with an additional quan- 

 tity of oxygen in the lungs, and thus forms the whole of the carbonic acid in question ; 

 and that, at the same time, a portion of oxygen is absorbed, which combines with the 

 carbon of the blood, and there generates the carbonic acid gas, or the oxide of carbon, 

 which forms a part of the matters discharged from the blood in the lungs. These pro- 

 cesses may vary, and either may predominate according to the state of the vital 

 influence at the time, under whose control they are immediately and completely placed. 



This view of the phenomenon in question seems to be fully supported by the experi- 

 ments of Dr. Edwards of Paris. They prove that the carbonic acid gas does not form 



G 



