742 ACIDS OF THE OXALIC SERIES, [App. 



As ordinarily precipitated from solutions of calcic salts by am- 

 raonic oxalate, calcic oxalate is quite amorphous, but in urinary 

 deposits it assumes a strong characteristic crystalline form, viz. that of 

 rectangular octohedra. In some cases it presents the anomalous forms 

 of rounded lumps, dumb-bells, or square columns with pyramidal ends. 

 It is insoluble in water, alcohol and aether, also in ammonia and acetic 

 acid. Mineral acids dissolve this salt readily, as also to a smaller extent 

 do solutions of sodic phosphate or urate. All the above characteristics 

 serve to detect this salt ; its microscopical appearance, however, is gene- 

 rally of most use for this purpose. 



The pure acid is prepared either by oxidising sugar with nitric acid, 

 or decomposing ligneous tissue with caustic alkalis. 



Succinic acid. H 2 C 4 H 4 O 4 . 



This is the third acid of the oxalic series, being separated from oxalic 

 acid by the intermediate malonic acid, H 2 C 3 H 2 O 4 . It occurs in the 

 spleen, the thymus, and thyroid bodies, hydrocephalic and hydrocele 

 fluids. 



According to Meissner and Shepard 1 it is found as a normal constituent of urine. 

 This is contested by Salkowsld 2 , and also by von Speyer. It seems probable how- 

 ever that since wines and fermented liquors contain succinic acid, and this latter 

 passes unchanged into the urine, that it may thus be occasionally present in this 

 excretion. 



Succinic acid crystallises in large rhombic tables, also at times in the 

 form of large prisms : they are soluble in 5 parts of cold water, and 2*2 

 of boiling, slightly soluble in alcohol, and almost insoluble in aether. 

 The crystals melt at 180 0., and boil at 235 C., being at the same time 

 decomposed into the anhydride and water. The alkali salts of this acid 

 are soluble in water, insoluble in alcohol and aether. 



Preparation. Apart from the synthetic methods, it may readily be 

 obtained by the fermentation of calcic malate, acetic acid being produced 

 simultaneou sly. 



Its presence is recognised by the microscopic examination of its 

 crystals, and its characteristic reaction with normal lead acetate. With 

 this it gives a precipitate, easily soluble in excess of the precipitant, but 

 coming down again on warming and shaking 3 . 



CHOLESTERIN. (C^H^O.) 



This is the only alcohol which occurs in the human body in the free 

 state. (The triatomic alcohol glycerin is almost always found combined 



1 Untersuch. uber d. Entsteh. d. Hippursaure. Hannover, 1866. 



2 Pfluger's Archiv, Bd. n. (1869) S. 367, and Bd. iv. (1871) S. 95. 



3 For further particulars see Meissner, op. cit. and Meissner arid Solly, Zeitschr. 

 /. rat. Med. (3) Bd. xxiv. S. 97. 



