OF RESPIRATION. 



form at length a most delicate and immense collection 

 of reticulated anastomoses. This extraordinary net- 

 work, penetrating the mucous web on every side, 

 closely surrounds the air cells, so that the prodigious 

 quantity of blood existing in the pulmonary vessels is 

 separated from the contact of the air by very fine mem- 

 branes only which Hales estimated as scarely T oVo of 

 an inch in thickness. 



141. As each ramification of the bronchiae possesses 

 a peculiar bunch or lobule of air cells, (139) so again 

 each of these possesses a peculiar system of blood 

 vessels, the twigs of which anastomose in the net-work 

 with one another, but scarcely at all with the blood- 

 vessels of the other lobules, as is proved by micros- 

 copic observations on living frogs and serpents, by 

 minute injections, and by the phenomena of vomicae 

 and other local diseases of the lungs. 



142. The common membrane investing the lungs 

 is the chief seat of a remarkable net-work of lymphatic 

 vessels* which run to numerous lymphatic or conglo- 

 bate glands,f carefully to be distinguished from a 

 neighbouring order of glands, called bronchial, that 

 are supplied with an excretory duct and are of the 

 conglomerate kind.;}; 



143. The thorax, which contains the lungs, has an 

 osseous and cartilaginous base, somewhat resembling 

 a bee-hive, throughout very firm and stable, but in 

 every part more or less moveable for the purpose of 

 respiration. 



* Mascagni, Histor. vasor. lywphaticor. Tab. xx. 



f Ibid. Tab. xxi. 



J Consult Portal, Mem. de VAcad. tics Scicnc. de Paris. 1780. 



J. G. Amstcin (Prses. Octingcr), DC ttsu ct actionc muscular, intercostal. 



