CONCRETIONS 461 



neither amyloid nor animal stareli. Those i'ormed in the central 

 nervous system may be of myelin or nenrojjlia origin. "- 



The small amount of material available prevents an accurate 

 analysis of the eor})ora amylacea; it is known that they are very in- 

 soluble in water, acids, alkalies, etc., behaving like coagulated protein 

 in this respect. p]ven hot concentrated nitric acid will not dissolve 

 them, according to Posner. This author considers lecithin and cho- 

 lesterol to be important constituents, and by Ciaccio's staining 

 method lipoids can be found in prostatic corpora amylacea."^ How- 

 ever, it is said by Bjorling ^* that the ordinary hyaline and granular 

 corpora do not contain fats or lipoids, but that a certain class of 

 "lipoid" prostatic concretions contain many granules of this nature. 

 The corpora 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 calcification, 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."^ The calculi consist usually of a mixture of 

 calcium phosphate and carbonate, associated Avith more or less organic 

 matter, including frequently cholesterol, but all the usual products of 

 proteolysis may be present because of the presence of trypsin. Oc- 

 casionally the calculi consist chiefly of calcium carbonate, which may 

 be almost pure."'"' Shattock °'^ has observed a pancreatic concretion 

 composed of calcium oxalate. Sodium phosphate and chloride, mag- 

 nesium phosphate, and proteins have also been found in these concre- 

 tions. Taylor "® describes a pancreatic concretion containing, accord- 

 ing to the analyst, chiefly silicate (!), a finding difficult to under- 

 stand or accept. 



Baldoni "^ found, on analysis of a stone weighing 3.1 grams, the 

 following percentage composition : 



Water .1.44 



Ash 12.f)7 



Proteins .3.40 



Free fatty acids 1,3. ,39 



Neutral fatty acids 12.40 



92 See Lafora, Virchow's Arch., 1911 f20r>), 29,5. 

 03 Posner, Zeit. f. ITrologie, 1911 (,5), 722. 

 ^i Tbid., 1912 (6), 30. 



95 Literature by Scheunert and Berpliolz, Zeit. plivsiol. Chom.. 1907 (-52), 33S. 



96 See Lazarus,' Zeit. klin. Med.. 1901 (,51), 530. Literatin-e. 

 9fia Rosenthal, Arch. f. Verdauunuskr., 1914 (20). G19. 



97 Brit. Med. .Tour., 1896 (i), 1034. 



98 Lancet, Dec. 18, 1909. 



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



