GLANDULAR CELLS OF THE FROG'S PANCREAS 349 



uents of the protoplasm of the pancreatic cell, and, if this is so 

 what are the mutual dependence among them, the mode of their 

 formation, and their relation to zymogen granules, are of much 

 importance not only for the study of the genesis of zymogen 

 granules, but also for the solution of the biological significance 

 of these structures in general. 



As material of the present investigation, the pancreas of Rana 

 temporaria was employed. 



2. THE NUCLEUS 

 Historical 



Ogata ('83) was the first to give fairly detailed information re- 

 garding the structure of the nucleus of the pancreas cell, though 

 R. Heidenhain ('80) previously noted the existence of the larger 

 nucleolus in it. Ogata worked on the amphibian pancreas, and 

 showed that the nucleus has a distinct, deeply basic-staining 

 boundary membrane with some thickenings or prolongations, 

 from which numerous, extremely delicate, granular threads 

 arise; the latter passing through the nucleus, and dividing it 

 into a number of fields. In these fields, independent of the 

 threads, there are one or more larger or smaller nucleoli, the 

 staining reactions of which enabled him to distinguish two kinds ; 

 some stained with haematoxylin, and others, generally single in 

 number, larger and stained by eosin. He termed the former 

 'karyosomes' and the latter 'plasmosomes.' 



These observations of Ogata were on the whole confirmed by 

 the studies of Kosinsky, Melissinos and Nicolaides ('90), Eberth 

 and Muller ('92), Ver Eecke ('95), Mouret ('95, '05), and many 

 others in the pancreas of various vertebrates. Mouret proposed 

 to designate Ogata's 'plasmosome' as 'nucleolus,' 'karyosomes' as 

 'pseudonucleoli' or 'amas nucleiniens.' 



Observations 



1. Chromatin network. The nucleus (figs. 13, 23, 28, 37), 

 stained with ordinary methods, e.g., with haematoxylin-eosin, 



