SPECIAL METHODS. 221 



The presence of organic substance in them is shown by the 

 fact that isolated globoids blacken strongly on heating. 

 They may be easily obtained by moving about on the cover- 

 glass sections which have been freed from fats and proteids 

 by successive treatment with ether-alcohol, \<f> caustic pot- 

 ash, and water. To obtain a pure white ash from the 

 globoids, very strong heating is necessary. 



If the residue left after strong heating be treated with an 

 ammoniacal solution of ammonium chloride, the character- 

 istic crystals of ammonio-magnesium phosphate are formed. 

 This shows at once the presence of phosphoric acid and 

 magnesium in the globoids. 



But if the globoids be treated with the ammoniacal am- 

 monium chloride solution before being heated, no formation 

 of ammonio-magnesium phosphate crystals occurs, evidently 

 because the organically combined phosphoric acid behaves 

 differently from the phosphoric acid set free by heating. 

 But the formation of large quantities of crystals of the double 

 salt mentioned takes place when sections, freed as above 

 from fats and proteids, are treated with a mixture of an 

 ammoniacal solution of ammonium chloride and sodium 

 phosphate. I have used in this case, with good results, a 

 reagent containing 10 parts of the two salts named and 10 

 parts of the officinal ammonia solution * to 100 parts of 

 water. 



391. The presence of calcium was shown by Pfeffer (I, 

 473) by the addition of an ammoniacal solution of ammonium 

 chloride and ammonium oxalate to the unchanged globoids. 

 There are then gradually formed the characteristic crystals 

 of calcium oxalate. By the addition of sulphuric acid, 

 the formation of the characteristic gypsum needles can be 

 brought about. 



d. Crystals. 



392. The crystals observed within the protein-grains con- 

 sists, like nearly all crystals observed within the vegetable 



* [This is of 16 Baum6, spec, gravity .960.] 



