12 E. A. Schäfer, 



The evidence tlien with respect to the striated border is much 

 in favoiir of its being- regarded as a part of the protoplasm of the 

 cell, having not improbably an active absorbing function. Like the 

 ectoplasm of many Protozoa it exhibits lines or streakings vertical 

 to the surface, probably indicating an obscure columnar structure.') 



As already stated the thickened border of the columnar cell 

 consists of two parts. The second part, upon which the striated 

 border proper rests, is a narrow highly refracting band of protoplasm'') 

 which more immediately bounds the vacuolated or reticular protoplasm 

 of the cell and serves as a connection between it and the striated 

 border, occupying in the columnar cell of the intestine a position 

 corresponding to that of the well known bright border of the ci- 

 liated cell. 



The structural appearances of the columnar cells such as are 

 here described are illustrated by the accompanying woodcuts which 

 have been reproduced from the ninth edition of Quain's Anatomy. 



The epithelium during ab Sorption. During active fat ab- 

 sorption, especially if the amount of fat in the chyme is relatively large, 

 the columnar epithelium cells become fiUed with globules of fatty matter 

 (Plate X, iigs. 4 and 5^). These globules are of variable size and may 

 occur in all parts of the cell, but they are generally largest ia the 

 part between the nucleus and the thickened border and are often 



movement in the columnar cells of the frog's intestine, and appears to think that 

 this may be of more general occuiTence than is usually supposed. I have myself 

 Seen once or tAvice in hardened specimens both from the dog and frog, smaU 

 groups of cells which were snrmounted by what certainly appeared to be true cüia 

 very fine and twice as long as the thickness of the striated border in adjoining 

 eells. But if cüia occur at all in the intestine of vertebrates, they are certainly 

 quite rare and exceptional. 



^) A similar border of verticaUy striated protoplasm is found in the large multi- 

 nucleated cells which are engaged in the process of absorption of bone. Kölliker, 

 Die normale Resorption des Knochengewebes, 1883. Taf. VIII. Fig. 87. 



*) Noticed by Erdmanu. Dissert. Dorpat 1867. 



^) The presence of fat in the epithelium ceUs dui'ing absorption is strangely 

 enough either ignored or altogether denied by some histologists (e. g. by Watney in 

 the paper already quoted, and by Klein, in bis Atlas of Histology) although it is 

 one of the most easüy demonstrated facts in Physiology. 



