GLANDULAR CELLS OF THE FROG'S PANCREAS 391 



No mutual relation could be found between the extent of the 

 network and the amount of zymogen granules. There are 

 cases in which the former is well developed, while the latter are 

 few in number, and vice versa. The zymogen granules are, 

 in general, not found in large numbers between the meshes of 

 the intracellular network. 



A similar network to that described above can be made mani- 

 fest by Flemming fixation and iron-haematoxylin staining 

 (figs. 100 to 105). It can scarcely be said that this method is 

 adapted to any animal, for the conditions under which the net- 

 work is fixed by Flemming' s fluid seem to depend either upon 

 the nutritive state of the animal, or the functional activity of 

 the cell, or some other unknown causes. I could demonstrate it 

 by means of the above method in sections of the pancreas taken 

 from an animal captured in the month of September. The 

 structure is located above the nucleus and consists of thick 

 or thin tortuous cords which form a network by interlacement 

 and anastomosis with each other. The cords are stained black 

 by iron-haematoxylin, and are, in most cases, solid, but some- 

 times canalized to a greater or less extent; the canaliculus is 

 bordered by two black lines, which are the optical section of 

 its wall. Just as has been observed in other preparations, the 

 network also emits longer or shorter cords or canaliculi which 

 pass through the granular zone; the longer ones often extending 

 to the cell border. It can further be seen that the darkly stain- 

 ing granules or droplets are either suspended on the cords or 

 canaliculi, or scattered through the granular zone, or even 

 attached to the distal or the lateral margin of the cell (figs. 101 

 to 104). These pictures are in full accord with those obtained 

 by means of the methods of Kopsch, Weigl, Sjovall, and Cajal, 

 with the sole difference that, in the Flemming preparation, the 

 cords are often canalized, which is to be regarded as due to the 

 dissolution of their substance, rather than to the real existence 

 of canaliculi. 



It must be noticed in this connection that the granules or 

 droplets seen in Cajal and Flemming preparations are per- 

 fectly distinct from those in Marchi preparations, although 



