19 



The observation of the foetal lung, however, affords most satis- 

 factory evidence of the separation of the lobulettes, and tends to 

 confirm the views here taken of the arrangement of the ultimate air- 

 tubes. 



The recent lung of a full-grown foetus presents on its surface no 

 appearance of air-sacs, or vesicles, or cells ; but if it be inflated, it 

 will present different appearances, according as the inflation has been 

 partial or entire. In a portion of lung only partially inflated, a 

 number of tubes will be seen terminating beneath the pleura in csecal 

 extremities, their light colour contrasting strongly with the sur- 

 rounding dark-coloured tissue. The exact arrangement of these 

 tubes may be sometimes seen. They will be found to exist in groups 

 or clusters, and are seen to pass from the csecal ends to a point, in 

 which they terminate, and where they all appear to join ; or, to de- 

 scribe them in the inverse direction, they pass from a point at some 

 distance from the surface, and radiate towards the pleura. The 

 tubes are seen to have numerous constrictions and bulgings ; they 

 terminate in extremities rounded, or nearly so. In a preparation of 

 this kind it is often easy to see the bronchial tube for a short dis- 

 tance before it terminates ; and not only is the terminal group of air- 

 sacs (lobulette) visible, but two or more of the previous ones arising 

 laterally from the bronchial tube may be also seen. The uninflated 

 lung-substance lying between the distended air-sacs is distinctly seen 

 when there has been only slight inflation ; and the isolated condition 

 of each group of sacs is very apparent ; the sacs passing from dif- 

 ferent points are seen radiating in different directions. In a lung 

 which has been fully inflated, the grouped appearance is lost, and 

 the ordinary condition of the distended lung is observed. 



If, in a foetal lung, we follow out a bronchial tube, we find that 

 the smaller branches of the tube have connected with them clusters 

 of little pyriform red- coloured bodies, which look very much like a 

 number of grapes attached to their stalks. In a foetus of six months I 

 have found it somewhat difficult to separate each individual body, but 

 in a full-grown foetus there is no difficulty in doing so; each little body 

 is attached to a short pedicle. If air be blown down a bronchial 

 tube leading to the exposed bodies, the latter become distended. 



The little bodies just described are the ready-formed groups of 

 air -sacs, or lobulettes ; the pedicle with which each is connected is 



c 2 



