Z S. SAGUCHI 



groups in the pancreas of the rabbit, many investigators who 

 have devoted themselves to the study of the pancreas have con- 

 centrated their attention on these structures — designated later 

 as Langerhans's cell-groups or islets — and there has been much 

 discussion as to their morphologj^, development, and signifi- 

 cance. This led to the formulation of various hypotheses, at 

 present far from being in agreement. The most complex and 

 difficult problem is that of the origin and ultimate fate of the 

 islet of Langerhans, especially its genetic relation to the acinus 

 tissue. Some believe that the islet is formed in an early embry- 

 onic stage by budding off and separating from the solid primitive 

 cell-cord, and that once formed, it may exist as a permanent organ 

 thi'oughout life. Others, while not denjdng its embryonic de- 

 velopment, hold that the islet may originate from the acinus 

 tissue of the adult pancreas. Laguesse and his supporters claim 

 that islet cells may be formed, on the one hand, by the trans- 

 formation of acinus cells and, on the other hand, by a reversion 

 to the latter, the two tissues being thus well balanced (balance- 

 ment theory). There are other observers who incline to the be- 

 lief that islet cells are derived from the duct epithelium. 



Decisive points in these discussions, especially of the problem 

 of the genetic relation between the islet and the acinus tissue, 

 have been the determination as to whether the islet is sharply 

 marked off from the acinus tissue by a connective-tissue capsule 

 or is in immediate contact with it, and whether or not the two 

 behave independently under experimental and pathological con- 

 ditions. Manj^ investigators seem to attach considerable im- 

 portance to the question of the existence or non-existence of a 

 capsule around the islet. We find it impossible to accept as ade- 

 quate the postulation that the existence of a capsule is a sign of 

 the independence of the islet, since it is difficult to decide whether 

 the capsule is perfect or not. Even when the islet appears to 

 be sharply separated from the- acinus tissue, it can hardlj" be 

 said that the two have no genetic connection. On the other hand, 

 it would be rash to assume a transition between the islet and the 

 acinus tissue merely because the two are sometimes found in 

 immediate contact, for there are many instances in which cells 



