Tin- i.r\ 467 



culus formed by the nir-tubcs and pulmnary vessels in entering the viscns ; 

 I. A posterior portion, more extrusive than the other two put together, 

 corresponding to the posterior mediastinum, and attached to that septum by 

 means of a fold developed around the organ, to form the pulmonary pleura; 

 this fold constitutes, posteriorly, a small serous ligament (Hijann-ntuin In/mn 

 piiliii'niitt), attached at once to the mediastinum and the posterior face of the 

 diaphragm. On this portion of the lung are remarked two antero-posterior 

 tissurcs: one, hollowed near the upper border of the organ, to receive the 

 thoracic aorta; the other situated lower, but not so deep, more marked in 

 the left than the right, and lodging the oesophagus. In the right lung this 

 mediastinal face ofters a small particular lobule, which is absent in the left. 



The base, or diajpkragwMtic fact of the lung, cut obliquely from above to 

 In-low, and before to behind, is concave, and moulded to the anterior face of 

 tin. diaphragm. On the right lung is seen the posterior face of the small 

 lobule noticed on the inner side, and a deep fissure excavated between it and 

 the principal lobe, for the passage of the posterior vena cava. 



The fin HI in it of the viscus, situated behind the first rib, presents a kind of 

 detached appendix, designated the anterior lobule of the lung. 



. The niijH f'mr border, thick, convex, and rounded, is lodged in the vertebro- 



1 channel or concavity. The inferior, much shorter and thinner, is 



<1< i ply notched at the level of the heart, and more so at the left than the 



right side. The posterior is elliptical, and everywhere circumscribed by the 



face of the diaphragm, which it separates from the costal and mediastiual 



laces. 



STRUCTURE. An external serous envelope, proper fundamental tissue, 

 fa in t'u, ,t<il and nutrient rewJs, lymphatic^, and nerves : such are the elements 

 which enter into the organisation of the lung. 



::ous ENVELOPE. This is the pleura ptilmonalis already describe. 1. 

 (There has also been described a stibserons coma //> tissue, containing a 

 large proportion of clastic fibres ; it invests the entire surface of the lung, 

 and extends between the lobules.) 



FUNDAMENTAL TISSUE. Pityxical diameters. The pulmonary tissue in 

 the adult is of a bright rose-colour; it has a deeper hue in the fietus which 

 lias not respired. Although soft, it is yet very strong and resisting, and 

 can with difficulty be torn. Its elasticity is remarkable ; it concurs in tin; 

 collapse the lung experiences when air is admitted to the. pleura! sues. It is 

 light : plunged in water, if healthy, it floats; this specific lightness 

 ought to be attributed to the air imprisoned in the. pulmonary vesiri -. 

 This may be proved by what takes place when the lung of a foetus is 

 intlati-d: heavier than water before that OJM ration, it then DMOOMI lighter, 

 because, notwithstanding all the manipulation that may be employed to cxj..-l 

 the air introduced into the pulmonary v. -i. -1. -. a e. rtain quantity always re- 

 mains. ( )n the other hand, the absolute weight of the lung is relatively more 

 considerable "** the adult than in the fietus. the \\\->\ re] i I -30th of 



the total mass ,,. body, while it is only 1-tiOth in the second. 



A knowledge of these facts may IMJ utilised in determining whether a -.riven 



lung has IK -longed to an animal which has ropiicd or l.as di.d In-fore hirtli. 



tissue is plunged in water, this test is called hydrostatic pulmonary 



docimacy ; if its relative weight is to be ascertained, it is designated 



pulmonary docimacy by w< ight. 



the physical characters of the fundamental ti.->uc of the lung; 

 v.i \\ill now study its anatomical char act i- 



An<i("ii,i---il ,-liiii-<ii-ti />. - The pulmonary tissue is partitioned into a great 



2 H 2 



