1886.] 



Proteid Substances in Latex, 



35 



This body is of great interest, as till lately no true albumin has 

 been described as occurring in plants. Ritthausen's albumins, 

 described by him in 1872,* as found in seeds, have been shown by 

 later observers, notably by Vines, to be rather globulins held in 

 solution by the neutral salts present in the seeds. Even Ritthausen 

 himself admits that the existence of a true albumin in seeds had not 

 been established satisfactorily as lately as 18 77. % In Martin's paper 

 already referred to, he describes a body which he has found to be 

 present in Papaw juice, which has the properties of an albumin. It is 

 coagulated on boiling, is not precipitated on dialysing an extract of the 

 juice, nor on saturating the solution by solid neutral salt. The body 

 just described as occurring in the latex of Brosimum seems to be 

 identical with this. It is noteworthy that both in the case of 

 Martin's albumin and that which has just been described, the albumin 

 appears to be a form of the circulating and not of the reserve proteid. 

 Boussingault's vegetable fibrin was probably this albumin coagulated 

 by the action of the hot alcohol used in its extraction. There 

 was no other body in the latex that would become coagulated 

 proteid. 



The other proteid found in this latex remained in solution after 

 boiling and filtering off the coagulated albumin. It was hence not 

 changed by heating ; it dialysed easily through a membrane, was pre- 

 cipitated but not coagulated by alcohol, and was precipitated by 

 saturation of its solution by solid MgS0 4 . It was therefore the same 

 body as described above as a constituent of the East Indian latex. 

 In the Brosimum latex there was a larger amount of it present, and 

 its reactions were therefore carefully confirmed. Besides those 

 already mentioned, two more peculiarities were noticed. In dilute 

 solution, a stream of C0 2 passed through it for several hours caused 

 a precipitate. On submitting it in concentrated or dilute solution to 

 the action of artificial gastric juice, it underwent conversion into a 

 true peptone, which gave a biuret reaction as readily as peptone pre- 

 pared by the same method from fibrin or other animal proteid. 

 There was not, however, during the digestion, any formation of acid 

 albumin. 



To protect the result from a danger of error arising from peptone 

 being present in the artificial gastric juice employed, the experiment 

 was performed as follows : — 



A certain amount of the proteid was taken from under alcohol, dis- 

 solved in water, and the solution decolorised by filtration through 

 animal charcoal. A solution of pepsin in 0'4 per cent, HC1 was 

 made and filtered. To a quantity of the proteid solution an equal 



Die Eiweiss-Korper der Getreidearten, &c," 1872. 

 f Loc. ext. 



X "Pfluger's Archiv," xv, 1877, p. 284. 



D 2 



