TNTXOr)T('TIONThih iiivestigatiori into the nature of hile capillary walls resulted f r o m thc obser*vation of lines in cross sections of bile capillaries in iron lieniatoxylin preparations of the liver of a pregnaiit female domestic pig. 'These liiics appeared a s delicate coiltinuat ions of the cell niernhrmm RCTOSY tlie r+cgioon which is knowii a s the lurtieii.ATaiiv investigators iii tlie past : McGi1lavr.y ( 1 864),Chrzonszczewski (1866), I V y s s (1866), A1iun.a (I 885), Xilne ( '09) ; have regarded the walls of [rile capillai*ies as struvtares independent of thc hepatic cells. Chrzonszcxewski F~I V the wall as it clear hortlei* 011 iiidigo carmine iiijcctecl I d e capillaries which \\'ere isolated bjteasing as well as in niicroscopic sections. Uilne ~*egai*cled the wall as a very thiu flatteiiecl epithelium ivi tli 1)ranches ~uri-ouiid~ng tlic iiiiiridiial hepatic cells. Hthriiig (186'7) considered the bile capillarj-\\-all as a coridensed mcnibi*aiie, surface layer, 01' cuticle of thc hepatic ccl Is which coiitiiines into a cnticnlaibordcr of the iiitci~lobiilar bilv ducts. The latter olxervation n a s made later bp Eppingcr ( '02) a i d by Bahl ( '30). It was regai.cietl by Eloerlh (1867) as a double cont oil red shiiiiiig inembi*aiic secre tccl by the This paper ir :I re~isioii of a dissertation submitttvl 111 p~t i a l fnlfillniriit of the rquirrments of n'iilgara LT!nivrrsit? for. the t l~g r c e of 1)octor of Phllosuphy. a Part of this work was tlenionstretrd at t h v Pittsliutgh meeting of the Aineriwn Association of kIl.%t(JIlllStS, April 15, 193% ( S c e 4n:it. Bcc , rol. 70. Suppl. no. 3, I,. 98.) : i -7 9