Page:Proceedings of the Royal Society of London Vol 60.djvu/366

Rh if a trace of a soluble salt of either barium, strontium, calcium, magnesium, or sodium be added, a pronounced coagulum is obtained on °h eating. This point will be returned to you in a subsequent section, but the similarity to dialysed serum-albumen may be pointed out, as that substance is stated not to coagulate when heated.* *§

The solution does not coagulate spontaneously on standing, neither will the addition of “ fibrin ferment (i.e., a nucleoproteidf) induce coagulation. It gives a typical xanthoproteic reaction, a violet with copper sulphate and potash, a dark heliotrope-puipie with cobalt sulphate and potash, and a faint yellow with nickel sulphate and potash. It also gives Frolide’s sulpho-molybdic reaction; I may, however, remark that I found that several substances chemically allied to proteids yield this reaction, which is therefore not diagnostic of proteids alone. An alcoholic solution of alloxan giv es with the solid plates a brilliant red coloration (Krasser’sJ reaction) similar to that produced with plates of serum-albumen. Negative results were obtained with the reactions associated with the names of Liebermann,§ Adamkiewicz, || and Millon.ff

The solution is neutral and laevorotatory («d == 52), and if treated with pepsin and a 02 per cent, hydrochloric acid, or by an alkaline solution of trypsin, for several days at 38° C. it does not peptonise.

Qualitative analysis shows that this substance does not contain phosphorus in its molecule.

It is precipitated from solution by mercuric chloride, silver nitrate, and lead acetate. These precipitates yield the same colour reactions as the original substance.

The precipitate formed by the addition of lead acetate, like that obtained by the addition of this substance to a proteid solution, redissolves on the passage of a current of sulphuretted hydrogen through the solution in which it is suspended, and judging by chemical tests alone, the nature of the substance is unchanged by the processes of precipitation and redissolving. Its physiological action is, however, markedly changed, as will be shown later on.

The original solution is readily precipitated by trichloracetic, phosphotungstic, phosphomolybdic acids, and by acetic acid and potassium ferrocyanide, as well as by salicylsulphonic acid ; the precipitate formed by this last substance is coagulated by heating in a manner similar to the coagulation produced by heating the precipitate resulting from the addition of this substance to a proteid

f Vide Halliburton, ‘ Journ. Physiol.,’ vol. 18, p. 306, 1895. + Krasser, ‘ Monat. fur Chem.,’ vol. 7, p. 673 ; ‘ Maly’s Jahresb.,’ vol. 16, p. 1. § Liebermann, ‘ Maly’s Jalires.,’ vol. 18, p. 8. (| Adamkiewicz, * Ber. d. deut. Chem. Gesell.,’ vol. 8, p. 761. 1 Millon, ‘ Comptes Rendus,’ vol. 28, p. 40.
 * Schmidt and Aronstein, ‘ Pfliiger’s Archiv,’ vol. 8, p. 75, 187A