llli: ORGANS OJ I HI l\\l.l: <.|;KM i..\ 





e to lie more and more a- i be righl and l.-ft of tin- In-art. With 



tin-it- ingrowth into tin- eaviti.-> of th.- dn->t (li-r. :\\\ /,,/,), tl;,-v pu-h 



before them the BerOUa lining of the latter, and thu 



I'leural OOWring tin- pleura pulmon.-ilk or th-- vi-ceral layer ol 



plell! 



During the secowl ttag* th.- organ, \\hid. up to thi- tim.- has the 

 typical Mructure of a hot ryoidal ;r land, assumes tin- dial-art.-! 

 pulmonary >tnu-tnri'. Tin- iin-taiin>r|lnsis begins in Man, as 

 Koi.i.iKKi; states, iii tin- >ixth month, and comes to a close in the 

 last month of pregnancy. There now arise close tot' . tin- 



!in<- tt-rminal tu- 



hnlcs of tin- bron- Ap 4-j 



fhial tree, on the 

 alveolar pass.! 

 and on their ter- 

 minal veMc-ular 

 cnlargem ents, 

 very numerous 

 Miiall e vagi na- 

 tions. But in di>- 

 tinction from the 

 railier ones, the-e 

 are not ron>t ricted 

 off from their 

 source of origin, 

 but c'oiiiiiiunirate 

 with the latter 

 by means of wide 

 oritic-es, and thus 

 constituto tin- <iir-celh or ]>nlnt<>it>ti'</ <tlff<>/i. Their :dy a 



third or fourth as ^reat in the embryo as in the adult; from this 

 KOLLIKER concludes that the inciva>e in the volume of the lun^ 

 from birth up to i-ompletf development of the botly is to be attributed 

 exch'.Mvely to the enlar-'. iii'-nt of the ve-icular elemeni> which 

 in the embryo. 



Tin- I'itli- !'i>il ///////;/ of tin- lun_ir i- \ arioii>ly iindiliel in dill. : 



us during development. In the whole bronchial tree the 

 epithelial cells increa-e in l..-iu r ht. ai'-juire in part a cylindrical, in 

 part a cubical form, and from the fourth month onward < KOI.I.IKEK) 

 have their free- surfaces OOVere I with cilia. In the air-sacs, on th- 

 contrary, the cells, which are arranged in a >ini:le layer, become 



Fig. 183. View of a reconstruction of the fundament of the lungs 

 of a human embryo (.V ,.f ([ > older than that of fig. 182. 



His. Magiiitii'<l ;>o iiiaintiten. 

 Ap, Artc-ri;i jmlnni:..; 



vesicle in process ' luir^ 



with an <-i>arterial bronchus leading ile and 



lower lobes of the right lung ; '. of the l-ft hiir^ 



with hyp:uti'ii;il ln-oiu-lnu leading to it ; U 1 , lower lobe of the 

 ing. 



