EXAMINATION OF BONE. 139 



sulphate solution gives a blue-violet color, which, however, 

 never shows a purple-red shade (distinction from peptone); 

 on heating to boiling the color becomes more red, if but little 

 copper sulphate solution has been added; if much copper 

 sulphate has been added, boiling produces no perceptible 

 color change. 



7. Boiling with Millon's reagent produces only a faint rose 

 or red coloration (it is advisable to first heat the gelatin solu- 

 tion to boiling, add a few drops of Millon's reagent, and then 

 heat again). Distinction from albumin, due to. the absence 

 of the tyrosine group in the molecule. The slight red color- 

 ation is to be attributed to admixture with albumoses or 

 peptone. 1 



8. The addition of bromine-water produces a voluminous 

 yellow precipitate of a viscous sticky nature. 



Gelatin possesses in the highest degree the property of 

 holding many precipitates in the state of the finest suspen- 

 sion, so that they pass through all filters, or it may even 

 prevent entirely the formation of precipitates. 



(a) Add to a portion of the gelatin solution in a test-tube 

 a drop or two of basic lead acetate: the solution remains 

 unchanged (gelatin is not precipitated by metallic salts in 

 general). Now dilute the mixture to about 30 cc. and pass 

 in hydrogen sulphide: there results a brownish-black fluid, 

 which passes through filter-paper unchanged; dilute a por- 

 tion of this with water: a clear light-brown solution results 

 from which no lead sulphide separates. 



(6) Dissolve a very small quantity of hypoxanthine in a 

 few cubic centimeters of dilute ammonia, divide the solution 

 into two approximately equal parts, and add to the one 

 (1) double the volume of water, to the other (2) double the 

 volume of the gelatin solution. To both portions add silver 



1 According to Van Name pure gelatin gives the Millon's reaction, see 

 Jour, of Expr. Med. 1897, 11, 117. O. 



