Sidney Klein 319 



may be mentioned in this connection the basal filaments of Solger, 94, 

 which have been shown by the researches of Bensley, 96, Gamier, oo, 

 Cade, oo, Zimmermann, 98, and others to be a structure common to 

 many sero-zymogenic cells. Bensley, 96, 98, has also shown that the 

 basal filaments correspond to the chromatin of the nucleus in their 

 staining reactions and like the latter contain iron in the form of an 

 organic compound and thus represent morphologically the substance 

 presumably of nuclear origin which Macallum, 95, long ago discovered 

 in gland cells of various sorts by means of staining reactions, and sub- 

 sequently confirmed by means of the microchemical reaction for iron. 

 As far as mucin is concerned no microchemical reaction has been, as 

 yet, discovered, which is effective in recognizing this substance in 

 isolated cells in sections. The work of P. Mayer, 97, has, however, 

 provided us with a number of new staining solutions which, while they 

 do not permit us to say whether a given cell does or does not secrete 

 mucin, yet furnishes evidence which may be of much value when taken 

 in connection with that from other sources. 



Up to the present no special attention has been directed to the ques- 

 tion of the presence of Macallum's prozymogen in the cells of Paneth, 

 either in the form of basal filaments or as a diffused compound in the 

 base of the cell, although several observers, notably Zipkin, 04, and 

 Nicolas, have called attention to the deeper staining of the protoplasm 

 of these cells as compared with neighboring cells. The results, more- 

 over, of attempts to discover experimentally, differences in the aspect 

 of these cells corresponding with phases of physiological activity have 

 not been decisive. Accordingly, at the suggestion of Professor Bensley 

 I undertook the reinvestigation of these structures in the hope that the 

 application of new staining and microchemical methods would reveal 

 new facts which would be of assistance in forming an opinion as to their 

 nature and their relationship to other intestinal epithelial elements. 



At a very early stage in the investigation the discovery was made that 

 in the opossum, Didelphys virginiana, the cells of Paneth occurred not 

 only in the glands of Lieberkiihn but also mingled with other epithelial 

 elements on the sides of the intestinal villi even at their very tips. This 

 remarkable fact, which possesses no parallel in any other mammal, so 

 far as is known, possesses so much significance in the interpretation of 

 the Paneth cells that a somewhat extended description is called for. 



The small intestine of the opossum is characterized by extremely long 

 villi and a very thin tunica mucosa. Corresponding to the latter the 

 glands of Lieberkiihn are very short and contain a scarcely recognizable 



