ANATOMY OF THE ALIMENTAEY CANAL. 
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Heidenhain (37), 1858, put forward a definite theory of fat-absorption, namely, that 
the epithelial cells are in connexion with the branched cells of the parenchyma, that 
there is a direct transition of these cells into real chyle-vessels, and that these structures 
are preformed ways which the fat traverses. He gave drawings of nucleated epithelial 
cells ending in processes, the processes containing a second nucleus, and filled with fat 
(fig. iv.). Heidenhain figured branched cells of the parenchyma connected with one 
another by processes (fig. vi.). In chromic acid, however, he found the cells were round 
and surrounded by a framework (fig. viii.). 
This theory of the connexion of the epithelial cells with the connective-tissue corpuscles 
was afterwards supported by Wiegandt (38), Balogh (39), Arnstein (40), Eimer (41), 
and Thanhofeer (57) ; but it was denied by Bindfleisch (42), Lipsky (43), Kolliker 
(44), Verson (45), and Basch (46). The connexion was necessarily denied by those who 
assumed an unbroken membrana propria, as Donitz (14) and Erdmann (34). 
Wiegandt (38), 1860, noticed the long processes attached to the epithelium of the 
frog’s intestine ; he could not find connective-tissue corpuscles with processes. Wie- 
gandt, however, considered Heidenhain’s view to be probably correct for the epithelium 
of the frog. 
Balogh (39), 1860, described processes in the epithelium of the rabbit’s intestine. 
Eberth (33), 1864, isolated the basement membrane which covers the villi. He found 
that the membrane has holes or gaps in it, and is attached to the blood-vessels (figs. i. 
& ii.). He described the membrana propria of Lieberkuhn’s crypts as a structureless 
membrane, with oval nuclei imbedded in it. Eberth figured short processes to some of 
the epithelial cells (fig. ix.). 
Donitz (14), 1864, spoke of the fat coming in in the form of a cloud, and said that 
the epithelial cells with processes are artificial products. This author denied the pre- 
sence of star-like or branching connective-tissue corpuscles in the mucosa ; and maintained 
that the epithelium is separated from the parenchyma by a glass-like membrane contain- 
ing no visible pores. 
Basslinger (47), 1858, found that in birds the lymphatic follicles are not sharply 
bordered, but that the follicular tissue may be found in the base of the villi, or even 
extending to their apices. 
His (48), 1862, showed that the tissue of the mucosa, including the villi, consists of 
a more or less close network of fine connective-tissue trabeculae, or branched cells, which 
form a framework attached to the blood-vessels ; in the meshes of the framework lymph- 
corpuscles are found. He called this tissue “adenoid.” His further showed that 
lymphoid follicles are not formations of a peculiar kind, but are richer collections of 
adenoid substance. He gave a drawing of the tissue of a villus which had been brushed, 
in which the reticulum is clearly seen (see His, fig. iv.) . 
Teichman (49), 1861, by his beautiful injections, showed the disposition of the chyle- 
vessels in the villi. He asserted that the chyle-vessels are closed. 
Becklinghausen (50), 1862, on the contrary, found that the material which he 
