38 S. SAGUCHI 



case the same, which fact may be taken advantage of in deter- 

 mining whether an islet is in the evolutive or in the involutive 

 period. Some difficulty is met with, however, by this deter- 

 mination; for example, in a case where the islet is rich in b cells, 

 it is hard to decide whether they are derived from a cells or from 

 e cells. On the other hand, I have not been able to perceive a 

 figure corresponding to the involutive change mentioned by 

 Laguesse which occurs so abruptly that it spreads rapidly over 

 the whole islet. In fact, solitary islet cells and small groups can 

 be found scattered throughout the pancreas of the frog, and it 

 would be obviously absurd to connect these with the involutive 

 change. 



FUNCTIONAL SIGNIFICANCE OF ISLET CELLS 



As to the functional significance of the islet there is consider- 

 able difference of opinion, which may be briefly summarized as 

 follows: 1) The islets have no function worth mentioning ( Nag- 

 ay o) . 2) They have something to do with the nervous system 

 (Langerhans, '69). 3) They belong to the lymphatic structure 

 (Kiihne and Lea, Sokoloff, Renaut, Mouret, Pischinger, Pug- 

 namt, Schlesinger, Katz and Winkler) . 4) They are either em- 

 bryonic remains or incompletely developed acini (Gibbes, Pier- 

 sol, Harris and Gow, Gianelli '00). 5) They are either exhausted 

 or temporarily modified parts of the pancreatic acini (Lewashew, 

 '86; Mankowski,'02; Vincent and Thompson, '06). 6) The islet 

 cells are real glandular elements and yield the secreted matter 

 to the pancreatic duct (a view advanced by Gianelli in 1898). 



7) The islets are either the parenchyma changed pathologically 

 or a stage of its regressive metamorphosis (Kasahara, Grineff, 

 '11; Fischer, '12); Dogiel ('93) believes them to be dead spots. 



8) The islets belong to that group of glands which are assumed to 

 take part in the so-called internal secretion. This is the view of 

 many investigators, such as Laguesse ('93, '95-'96, '09-' 10), 

 Diamare ('99), Ebner ('99), Hansemann ('02), Pearce ('02-'03), 

 Heiberg ('09), Piazza ('11), and others. 



It is evident, from these various views advanced by different 

 investigators, that the islet is a tissue, the functional significance 



