190 



OF ABSORPTION AND SANGUIFICATION. 



been directed to the structure of these columnar investing epithelial cells; 

 and if the observations of v. Thauhoffer 1 be correct, our knowledge of the 

 mode of absorption of various substances, and especially of those of an 

 oleaginous nature, will be materially simplified. According to these investi- 

 gations, the investing cells 2 of the villi (c, Figs. 78 and 79, a, Fig. 80) are 



FIG. 77, 



A perpendicular section through the wall of the Processus Vermiformis (Man), a. Lieberkiihnian 

 glands. 1. Solitary follicle, c. Lacteal vessels, surrounding but not penetrating the follicles. At d, 

 are seen the larger efferent vessels, provided with valves. 



of columnar form, with a broad free, and a narrower attached extremity. 

 The free extremity presents a thickened, bright, and highly refractile border 



1 v. Thanhoffer, Pfliiger's Archiv, 1874, p. 391. 



2 See Heidenhain in Moleschott's Untersuchungen, Bd. iv, 1858, p. 251 ; and 

 Brucke in id. Bd. viii, 186:2, p. 4!)5; and in Denksehrift. d. k. Akad. d. Wiss. zu 

 "Wien, Bd. vi, p. 105. Also Verson in Strieker's Human and Comparative Histology, 

 Syd. Soc. Transl., vol. i, 1870, p. 573. Kanvier, art. Epithelium in the Nouveau J>ic- 

 tionnaire de Medecine, t. iii, 1870. v. Thanhoffer, Pfliiger's Archiv, 1874, p. 391. 

 These epithelial cells were described by MM. Gruby and Delafond (C. llendus, 1843, 

 ir.'5), as possessing cilia on their free margin; but Kolliker, Funke, and more re- 

 cently Schultze, considered this appearance as illusor}', and produced l>y the thick 

 membrane closing the free extremity of the cell being perforated by verv delicate 

 pores or canals, whilst after death it split up in such a manner as to rese.ml>l<- a bundle 

 of cilia (Kolliker, Mikroscop. Anat., 1800, p. 329). Balogh, agreeing with Kolliker 

 as to the lines in question being canals, differed from him in believing them to be not 

 pre-existent, but merely the indications of the passages made by the molecules of fat 

 in penetrating the delicate tissue occluding the mouth of the cell ( Moleschott's 

 Unters ., lid. vii, 1801, p. 556). Brettatier and Steinach, on whose observations the 

 -tniements of Brucke, Iloidenhain, and other later authors are founded (Brettauer 

 and Steinach, Sit /.ung>bericht d. k. Akad. d. wissen. zu Wien, 1857, P.d. xxiii, p. 

 ''^''>\, maintained that the a]i]iarent cilia are prolongations of the cell-contents, the 

 cells themselves terminating with a smooth circular margin. They described the 

 columnar arrangement as broadest and most distinct in fasting animals, whilst in cells 

 tilled with fat it diminishes to one-half or one-third of its former breadth, and the 

 -tri;e disappear, s<> that only a bright narrow rim or border is left. Lastly, Wiegandt 

 is stated in Canstatt's .Jahre.-bericht for 1802, p. 32, to view the cilia as merely the 

 optical expression of stri;e or wrinkles. 



