1886.] 



Proteid Substances in Latex. 



37 



It is insoluble in distilled water or in sulphate of soda solution, but is 

 soluble in weak acids or alkalis. Its precipitate in distilled water is 

 changed by contact with alcohol into a white stringy mass. It gives 

 the xanthoproteic reaction, and that with copper sulphate and potassic 

 hydrate. Fischer* has observed also that the fluid contents of the 

 sieve tubes in Gucurbita become coagulated on heating. 



The first investigation of the extract prepared as above, was not 

 easy on account of the difficulty of getting rid of the soluble phos- 

 phates, which were found to be present in considerable quantity. 

 They were removed by warming with ammonia, but the last traces 

 were very hard to throw down. The liquid finally, however, ceased 

 to give a precipitate with ammonium molybdate. Besides the phos- 

 phates the salts present were sulphates and chlorides, but both were 

 much smaller in amount than the phosphates. 



Having freed the extract from phosphates, it was found to coagu- 

 late on boiling, and the coagulum gave the xanthoproteic reaction. 

 On heating it more slowly an opalescence was found to appear at 74 — 

 76° C, which was replaced by a precipitate at about 80° C. After 

 filtering this precipitate off, no further opalescence took place up to 

 boiling point. Dialysis for some time caused a precipitate, though 

 not a very bulky one. Saturation of the neutralised liquid with 

 MgS0 4 gave a precipitate, arid a stream of C0 2 through a weak 

 solution did the same. These reactions, taken together, indicated the 

 presence of a globulin, of pretty much the same character as that 

 found in Gucurbita by Zacharias and Fischer. They were not, how- 

 ever, quite conclusive, as several of the methods used would have 

 thrown down, if it were present, the body described as occurring in 

 lafcices examined before. This body was therefore looked for and 

 found. After getting rid of the globulin by heating and filtering, the 

 liquid gave the same reactions as those described before as belonging 

 to that body. The dialysis especially was well marked, alcohol 

 giving a proteid precipitate readily with the liquid outside the 

 dialyser. The globulin was not so readily isolated, but it proved 

 possible to get it by dialysis. It was not present in such large 

 quantity as the other, and was more readily precipitated completely 

 from its solution by saturation with solid MgS0 4 , for the fluid, when 

 both were present, gave a xanthoproteic reaction after it had ceased 

 to give a precipitate on boiling. It was also precipitated on very large 

 dilation. 



Hence in the extract of Manihot are two proteids, one being 

 globulin in nature and agreeing in its reactions with that of Zacharius 

 and of Fischer ; being satisfactorily separated from the other without 

 injury only by dialysis ; both giving precipitates on saturation with 

 solid MgS0 4 . A similar body to this globulin has been described by 

 * " Eerichte d. deutsch. bot. Gesell.," vol. ii, No. 7, 1885. 



