ABSORPTION FROM THE DIGESTIVE CAVITY. 



191 



surrounding the open mouth of the cell. The border varies in thickness and 

 breadth in different cells, even of the same villus; and when the cells mv 

 examined from above, their margins seem to be continuous with each other, 

 so that a kind of mosaic is formed. Immediately internal to the border is 

 a row of processes formed of the protoplasmic contents of the cell, which in 

 mammals are rod-like, but in frogs, especially when examined in winter, are 

 ciliaform. The processes stand erect during life, but quickly disappear after 

 death, being replaced by a globular swelling projecting from the mouth of 

 the cell, occasioned by the imbibition of water. 



The contents of the cells during fasting are a mass of clear protoplasm, 

 and a bright nucleus with nucleolus; but during digestion, especially of 

 substances containing fat, the protoplasm becomes cloudy or granular, from 

 the entrance of the molecules of oil into its substance ; a process that is 

 facilitated by the movement of the processes above described. The attached 

 extremity runs out into two kinds of processes, one of which is continuous 

 with stellate corpuscles (d, Fig. 78), forming a lymph caualicular system in 

 the connective-tissue matrix of the villus, which opens into the central lacteal 

 vessel (e), thus affording a direct means of entrance for the fat-molecules 

 into the absorbent system, and explaining the occasional introduction of solid 



FIG. 78. 



FIG. 79. 





YIG. 78. Diagrammatic representation of the Origin of the Lacteals in a Villus, according to Funke: 

 e Central lacteal; d. Connective-tissue corpuscles with communicating branches; c. Ciliated columnar 

 epithelial cells, the attached extremities of which are directly contiguous with the connective-tissue 

 corpuscles. After Funke. 



FIG. 79. Origin of the Lacteals according to Letzerich. The cells marked n, are cup or goblet-cells, 

 and are seen to he intercalated amongst the columnar epithelial cells, and to communicate with a deli- 

 cate plexus, 6, that opens at various points into the central lacteal, c,f; d, Layer of clear connective 

 tissue; e, connective tissue with numerous nuclei. 



FIG. 80. a. Body of Columnar cell from small intestine. 6. Smooth border of cell. c. Protoplasmic 

 processes, d. Connective-tissue processes, e. Nerve-fibre penetrating the cell to join the nucleus. </,/. 

 Ganglion cell. 



particles into the circulating current, whilst the other (e, Fig. 80) appears 

 to be nervous tissue, since it is connected with a corpuscle resembling a gan- 

 glion-cell, and has the chemical relations of nerve. It penetrates the foot of 

 the cell, and has been traced to the nucleus. Interposed at variable distances 

 between the ordinary columnar cells, are peculiar oval cells, known as Cup, 

 or Goblet-cells (Fig. 79, a). These have been regarded by Letzerich 1 as the 

 true commencements of the absorbent system, and he traces a connection 



1 Virchow's Archiv, Band xxxix, 167, p. 435. 



