228 Royal Society. — Linncean Society. 



process to be more simple than is imagined, and more within the 

 reach of anatomical than chemical investigation. The present 

 theory among chemists, he states, is, that respiration decarbonizes 

 the blood, a volume of oxj'gen and nitrogen being received into the 

 lungs at each inspiration, and returned measure for measure, the 

 oxygen only being partly converted into carbonic acid ; thus pro- 

 ving, as they suppose, tliat no part of the atmospheric air breathed 

 is retained. This theory Sir E. Home considers as satisfactory, 

 supposing it to be supported by the structure of the lungs themselves, 

 and taking it for granted that the blood requires no other change 

 for its purification. But when it was devised, no accurate exami- 

 nation of the cellular structure of the lungs had been set on foot; 

 and it is the object of tlie present communication to explain their 

 mechanism, and ascertain to what extent it is fitted for the pro- 

 cesses this theory requires. 



The author began the investigation of this subject by inquiring 

 into the circulation of blood through the lungs; and by the assist- 

 ance of Mr. Russel, of St. George's Hospital, he procured injections 

 of their veins and arteries, capable of being rendered objects of 

 microscopical examination by Mr. Bauer. 



The first fact discovered, was, that though an injection introduced 

 by the pulmonary artery was found to return by the trunks of the 

 pulmonary veins ; yet, when thrown in by the veins it does not re- 

 turn by the arteries. The next fact ascertained, was, that the dis- 

 tention of the air-cells produces an interruption between the arterial 

 and the venous circulation, the blood being carried no further than 

 the small arterial branches surrounding the air-cells. Sir Everard 

 next proceeds to describe the air-cells and parts surrounding them, 

 from drawings made by Mr. Bauer. The branches of the pulmonary 

 artery accompanied by larger and more numerous branches of the 

 pulmonary vein, are seen ramifying behind the internal membrane 

 of each cell: the latter have valves at regular intervals, and there 

 are numerous absorbents supplied also with valves. The injection 

 was found to have stopped short of the termination of the artery, 

 and the space beyond to be filled with gas. 



The conclusions deduced by the author from this investigation 

 are unfavourable to the received doctrine of simple decarbonization ; 

 conceiving the structure thus developed as better adapted to receive 

 supplies from the atmosphere, and transmit them to the heart. He 

 considers that the carbonic acid detected by Professor Brande in 

 urine and perspirable matter, must have been formed in the blood 

 circulating through the arteries, and have derived the oxygen in 

 its carbonic acid from the lungs. He considers further, that the 

 carbonic acid carried off in respiration is furnished from such venous 

 blood as has acquired it during the process of digestion ; having 

 shown on a former occasion that soon after that process has com- 

 menced, the oxygen employed in it unites with carbon. 



LINN.SAN SOCIETY. 

 Feb. 6. — Several vacancies were declared in the list of the Foreign 

 members, and the names of various distinguished Foreign naturalists 



were 



