36 Swale Vincent and F. D. Thompson. 



We have made an attempt to bring about the conditions induced 

 by secretin by means of pilocarpine, but without success. The whole 

 tissue appeared shrunken, and the whole gland somewhat exhausted but 

 there were no more Islets than in the normal tissue. 



V. The Reconstruction of Alveoli from Islets. 



As a result of very careful embryological work in the sheep, 

 Laguesse^) has described two categories among the islets. 1. Those arising 

 from the solid cords, or from the wall of the primitive pancreatic tubes, 

 the „primary islets". 2. Those derived from a transformation of the 

 secreting cavities. 



The first category arises from the „cellules troubles" of the first 

 solid ramified cords. The production of these primary islets soon 

 ceases, and according to Laguesse they finally disappear. 



The secondary islets are formed from the secreting cavities them- 

 selves, both simple and lobed. There is a gradual transformation ot 

 a' great number of cavities into solid islets, and the process is described 

 by Laguesse in great detail. 



A further process occurring while the animal is still in the em- 

 bryonic condition is described by Laguesse. This is the regression of 

 the secondary islets and reconstruction of acini. The islets in regression 

 are faded or irregular in contrast with the plump condition in early 

 embryos. Their cells are small with indistinct outlines. Then at certain 

 points the islet opens into a canal and the lumen penetrates into the 

 islet. Zymogen granules gradually become deposited and so new acini 

 are formed. „Par une sorte de balancement régulier, toute cavité 

 sécrétante, après avoir fourni un certain nombre de lois une sécrétion 

 externe, se transformerait temporairement en îlot pleine endocrine et 

 déverserait alors dans les vaisseaux primitifs, et recommencerait indéfini- 

 ment â parcourir le même cycle." 



'I'll lis from morphological and embryological teachings, we are pi'e- 

 pared to anticipate that acinus may be converted into islet, and islet 

 into acinus concomitantly with vaiiatioiis in the physiological conditions. 



') liOr,. cit.. 



