of the black Bronchial Glands, ^c. 165 



common life. It is admitted, that the oxygen of atmospherical 

 air passes through the pulmonary air vesicles, or cells, into the 

 system of blood vessels; and it is not improbable, that tlirough 

 the same channel various matters contained in the air may be 

 introduced. But it is highly reasonable to suppose, that the 

 particles of charcoal should be retained in the minutest rami- 

 fications of the air tubes, or even in the air vesicles, under 

 various circumstances, to produce the coloured appearances 

 on the surface, and in the substance of the lungs, as above 

 described. It must also be considered, that innumerable 

 absorbent lymphatic vessels take their rise in the bronchial 

 tubes : for the lungs are more richly stored with lymphatic 

 vessels than any other organ, excepting the liver. When I 

 compared the black lines and black net-like figures, many of 

 them pentagonal, on the surface of the lungs, with the plates 

 of the lymphatic vessels by Cruickshank, Mascagni, and 

 Fyffe, I found an exact resemblance. And when I found that 

 these vessels contained charcoal, I judged that it was fair to 

 infer, that the lymphatics of the lungs absorb a variety of very 

 different substances, and especially this coaly matter, which 

 they convey to the bronchial glands, and thus render them of 

 a black, or dark blue colour- Hereafter, among other enquiries, 

 the colour of the large trunks of the lymphatic vessels, just 

 before they enter the bronchial glands, and just as they pass 

 out of them, ought to be observed. Also the effect of the 

 charcoal thus conveyed into the thoracic duct, or directly into 

 the blood by the lymphatics from the black glands, is, I pre- 

 sume, worthy of attention. 



According to this theory, we can account reasonably for the 

 absence of the black colour of the bronchial glands, and of the 



Z 3 



