PANCREATIC CALCULI 387 



but this is the exception. It seems probable that corpora amy- 

 lacea are usually proteid concretions/ and neither amyloid nor 

 animal starch. 



The small amount of material available prevents an accurate 

 analysis of the corpora amylacea ; it is known that they are 

 very insoluble in water, acids, alkalies, etc., behaving like coag- 

 ulated proteid in this respect. Even hot concentrated nitric 

 acid will not dissolve them, according to Posner. This author 

 considers lecithin and cholesterin to be important constituents, 

 which view does not seem to have been confirmed. The cor- 

 pora amylacea of the lateral ventricles seem to consist chiefly 

 of calcium salts deposited in a concentric arrangement through 

 the medium of an organic basis. Posner considers that the 

 presence of lecithin in prostatic corpora prevents their calcifica- 

 tion, although this change occasionally does occur. 



OTHER, LESS COMMON CONCRETIONS 



Pancreatic Calculi. The cause of the formation of stones 

 in the pancreatic duct is not definitely known, but apparently 

 infection is the most important factor, since simple experimental 

 stasis will not cause their formation. 2 The calculi consist usually 

 of a mixture of calcium phosphate and carbonate, associated 

 with more or less organic matter, including frequently choles- 

 terin, but all the usual products of proteolysis may be present 

 because of the presence of trypsin. Occasionally the calculi 

 consist chiefly of calcium carbonate, which may be almost pure. 

 Shattock 3 has observed a pancreatic concretion composed of 

 calcium oxalate. Sodium phosphate and chloride, magnesium 

 phosphate, and proteids have also been found in these concre- 

 tions. 



Baldoni 4 found, on analysis of a stone weighing 3.1 grams, 

 the following percentage composition : 



Water . 3.44 



Ash 12.67 



Proteids 3.49 



Free fatty acids 13.39 



Neutral fatty acids 12.40 



Cholesterin 7.69 



Pigments and soap 40.91 



Undetermined 6.01 



1 Eamsden's observations (Proc. Koyal Soc., 1903 (72), 156) on the precipi- 

 tation of proteids by the action of surface contact may have some bearing on 

 the formation of such proteid concretions. 



2 See Lazarus, Zeit. klin. Med., 1904 (51), 530. Literature. 



3 Brit. Med. Jour., 1896 (i), 1034. 



4 Schmidt's Jahrb., 1900 (268), 210. 



