CORPORA A.^rVLACEA 465 



give all the amyloid reactions characteristically, but the corpora 

 amylacea of the lungs are much more likely to do so (Stumpf).^' It 

 seems improbable that these bodies, which occur in the prostate of 

 every adult, can be the same as the amyloid, which is seldom observed 

 except as the result of serious processes of tissue destruction. Accord- 

 ing to their structure they obey the usual laws of the formation of 

 concretions, having a central nucleus and a structural framework of 

 different composition from the chief substance. It seems most prob- 

 able that they should bo interpreted as simple concretions of protein 

 nature, which form under certain conditions when a nucleus of some 

 sort (usually pigment, degenerated cells, or inorganic crystals) exists 

 in a stagnating, protein-rich fluid. At limcs the resulting concretion 

 may be of such a physical nature that it absorbs iodin readil}^ (just 

 as they often show a marked absorption-affinity for pigments), and 

 occasionally it may react metachromatically with methyl-violet, pos- 

 sibly because of the presence of chondroitin-sulphuric acid derived 

 from the mucin of the cavities where the concretions form, but per- 

 haps for some other unknown reasons. Occasionally pure amyloid 

 may form in the tissues typically concentric (or even crystalline) 

 bodies, as in Ophiil's case, but this is the exception. It seems prob- 

 able that corpora amylacea are usually protein concretions,^'^ and 

 neither amyloid nor animal starch. Those formed in the central 

 nervous system may be of myelin or neuroglia origin.-^ 



The small amount of material available prevents an accurate 

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

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

 in this respect. Even 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, 



" Virchow's Arch., 1910 (202), 134. 



" Ramsden's observations (Proc. Royal Soc, 1903 (72), 156) on the precipi- 

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

 the formation of such protein concretions. 



2« See Lafora, Virchow's Arch., 1911 (205), 295. 



" Posner, Zeit. f. Urologie, 1911 (5), 722. 



28 /bid, 1912 (6) 30. 



2^ Literature by Scheunert and Bergholz, Zeit. phj'siol. Chem., 1907 (52), 338. 



30 



