Latex and its Functions . 
195 
I. Proteids and the Coagulation of Latex. 
Coagulation of latex is now known to be brought about 
by the proteid contained in it passing from a soluble to an 
insoluble state, whereby the particles of caoutchouc, &c. in 
suspension are gathered together into clots; or, as Bififen 
graphically puts it in a paper 1 on the subject, the coagulating 
proteid ‘ gathers up the rubber particles in the same way 
as the white of an egg gathers up particles in suspension 
when clotted for the purpose of clearing jellies.’ Consequently 
the conditions of coagulation depend upon the kind of proteid 
present in the latex. If it be globulin or albumen, then 
clotting should be brought about readily by heating; if 
albuminate, by neutralization. 
Hevea brasiliensis . The proteid of this latex is said to be 
albumen, as is assumed in Biffen’s paper 2 . Its coagulation 
has been studied in some detail in Ceylon, primarily for the 
purpose of devising the best means of preparing commercial 
indiarubber by the clotting method. The results suggest 
rather an albuminate than albumen as the particular proteid 
present. 
The latex, such as is collected from incisions in the trunk 
of the tree, mixes in all proportions with water, and as it 
is too thick for experimental purposes when pure, it has 
usually been employed diluted ten times with water. This 
diluted latex is not clotted by heat—no change takes place 
in it after boiling for several minutes; it shows a great 
contrast in this respect to the latex of Manihot Glaziovii , 
Miill.-Arg. (Ceara Rubber), which in the diluted form clots 
readily when boiled, and fairly quickly in the cold. This 
latter latex contains a globulin. 
If a trace of acid be added to the hot Hevea latex, clotting 
takes place immediately; on the other hand small quantities 
of alkalies postpone the coagulation indefinitely. It is not, 
however, necessary to add the acid to the hot latex; it brings 
1 Biffen, Annals of Botany, xii, June, 1898, p. 170. 
P 
2 loc. cit., p. 170. 
