470 DIGESTION. 



The pancreatic gland is similar in certain respects to the parotid 

 gland. The secreting elements of the former consist of nucleated cells 

 whose basis forms a mass rich in proteins, which expands in water and in 

 which two distinct zones exist. The outer zone is more homogeneous, 

 the inner cloudy, due to a quantity of granules. The nucleus lies about 

 midway between the two zones, but this position may change with the 

 varying relative size of the two zones. According to HEIDENHAIN l 

 the inner part of the cells diminishes in size during the first stages of 

 digestion, in which the secretion is active, while at the same time 

 the outer zone enlarges owing to the absorption of new material. In the 

 later stage, when the secretion has decreased and the absorption of the 

 nutritive bodies has taken place, the inner zone enlarges at the expense 

 of the outer, the substance of the latter having been converted into that 

 of the former. Under physiological conditions the glandular cells are 

 undergoing a constant change, at one time consuming from the inner 

 part and at another time growing from the outer part. The inner 

 granular zone is converted into the secretion, and the outer, more homo- 

 geneous zone, which contains the repairing material, is then converted 

 into the granular substance. The so-called islands of LANGERHANS 

 are related to the internal secretion or contain a substance taking part 

 in the transformation of the sugar of the animal body. 2 



The chief portion of protein substances contained in the gland con- 

 sists, it seems, of a protein insoluble in water or neutral salt solution and 

 of nudeoproteins, while the globulin and albumin occur only to a slight 

 extent as compared with the nucleoproteins. Among the compound 

 proteins is tjie substance studied and isolated by UMBER but previously 

 discovered by HAMMARSTEN 3 and called a-proteid. This nucleoprotein 

 contains, as an average, 1.67 per cent P, 1.29 per cent S, 17.12 per cent 

 N, and 0.13 per cent Fe. It yields ( #-proteid on boiling, which is much 

 richer in phosphorus than the nucleoprotein. The native proteid (a) is 

 the mother-substance of guanylic acid; according to UMBER it dissolves 

 on pepsin digestion without leaving any residue, and yields on trypsin 

 digestion guanylic acid on one side and proteoses and peptones on the 

 other. It can be extracted from the gland by a physiological salt solution, 

 and is precipitated by acetic acid. Besides this compound protein the 

 pancreas must contain at least one other protein which is the mother- 

 substance of the thymonucleic acid obtainable from the pancreas. 



Besides these protein substances the gland also contains several 

 enzymes, or more correctly zymogens, which will be discussed later. 



1 Pfluger's Arch., 10. 



2 See Diamare and Kuliabko, Centralbl. f. Physiol., 18 and 10; Rennie, ibid., 18; 

 Sauerbeck, Virchow's Arch., 177, Suppl. 



3 Umber, Zeitschr. f. klin. Med., 40 and 43; Hammarsten, Zeitschr. f. physiol. 

 Chem., 19. 



