464. 



On the colouring Matter of the black Bronchial Glands and of the 

 black Spots of the Lungs. By George Pearson, M.D. F.R.S. 

 Read February 25, 1813. [Phil. Trans. 1813,^. 159.] 



It is well known that in men the bronchial glands that are situated 

 near the bifurcation of the trachea are of a very dark colour; that in 

 infancy the lungs in general have little or no such colour ; that at 

 the age of eighteen or twenty they have a mottled or marbled 

 appearance, from black or dark blue spots, lines and points dissemi- 

 nated through them immediately under the membranous covering, 

 and that this appearance becomes darker and darker as persons ad- 

 vance in age ; and that the same black spots are also observable 

 throughout the whole interior substance of the lungs when cut. 



It has been conjectured by some persons that this appearance is 

 owing to sooty matter taken in with the air during respiration, and 

 accumulated in proportion to the duration of life ; but in reply to 

 this supposition it has been objected by others, that the same degree 

 of blackness is not observable in brute animals, and that the theory 

 is not supported by any accurate observations of the proportional 

 want of intensity in those persons who might be supposed to have 

 lived less exposed to soot by permanent residence at a distance from 

 any large town, and from any other considerable consumption of 

 fuel. 



Dr. Pearson professes himself to be of the former opinion, and 

 adduces a series of experiments to prove that the black matter in 

 question is actually charcoal. In order to collect the subject of his 

 experiments, the black glands in which it is contained are dissected 

 out, and by washing are freed as far as possible from extraneous 

 matter. The colouring substance is then partly pressed out, diluted 

 with water, and found to subside from it as a black deposit. By 

 boiling the black glands in caustic potash the whole structure is 

 destroyed, but the black matter is not dissolved, and after a sufficient 

 length of time subsides from the fluid. By muriatic acid also the 

 glands are dissolved, and black matter is deposited from the solution. 

 Nitric acid also dissolves the glands, but not the black matter which 

 in this case floats on the surface. 



By corresponding experiments on the substance of the lungs the 

 same black deposit is obtained, but in much smaller proportion than 

 from the glands. 



The black matter thus collected and subsequently dried, having 

 been found to yield carbonic acid by deflagration with nitre or 

 oxymuriate of potash, Dr. Pearson considers himself warranted in 

 concluding that it is charcoal in an uncombined state ; that it is 

 admitted along with the air in respiration ; that it is retained in the 

 minute ramifications of the air-tubes, and conveyed by the absorbents 

 to the bronchial glands. 



