GLANDULAR CELLS OF THE FROG'S PANCREAS 399 



the chromatic substance being limited to crescent-shaped or an- 

 nular corpuscles, which are situated upon or in the protoplasmic 

 substratum of the body. Those structures, which are described 

 under the name of mebenkern' by various investigators, Ogata, 

 Eberth and Muller, and others, belong, in part at least, to this 

 category. I will return to this question further on. 



5. MITOSIS 



Since the pancreatic cells undergo physiological degeneration, 

 it is a matter of course that they must be supplemented in some 

 way; this is effected by mitosis, which varies more or less accord- 

 ing to individual cases. The nucleus preparing to divide by 

 mitosis migrates upward and comes to lie about midway between 

 the base and the distal end of the cell (fig. 106) ; the cy top 1 asm 

 becomes stained more or less pale, the position and arrange- 

 ment of zymogen granules and mitochondrial filaments differ- 

 ing in no way from those of resting cells (figs. 106, 107). The 

 plane of cleavage being vertical (fig. 108), the daughter cells 

 acquire both zymogen granules and chondriocontes (fig. 109). 

 I have never been able to observe that the latter are increased 

 in number by division or that an equal amount of them passes 

 into each of the daughter cells, as assumed by some. Sometimes 

 there are seen glandular cells with two nuclei; whether they are 

 produced by mitosis or amitosis I was unable definitely to 

 determine. 



The mitotic figures were observed, in the pancreas, by Gaule 

 ('80), Nussbaum ('82), and by many of the subsequent investi- 

 gators (Bizzozero and Vassale, '87, Platner, '89, Steinhaus, '90). 

 Podwyssozki ('87) believes to have found mitosis in young 

 animals, while Eberth and Muller ('92) deny its occurrence in 

 any case. The most curious view concerning the regeneration 

 of the pancreatic cell is advanced by Ogata ('83). This author 

 believes that the plasmosome of the nucleus passes out into the 

 cytoplasm and there forms the so-called 'nebenkern,' which is 

 transformed through gradual increase into a new cell, while 

 the old one undergoes degeneration. The result of this process 



