PROTEIN- COMPOUNDS. 329 



The protein-compounds, when submitted to dry distillation, 

 when allowed to putrefy, and when decomposed by oxidising agents, 

 behave precisely in the manner of the histogenetic substances gene- 

 rally, which has been already described (pp. 322-3) ; giving rise to 

 the above-named products of decomposition, although in different 

 relations of quantity. 



All protein-compounds contain sulphur, which can be very rea- 

 dily detected in these substances both in their natural state, and when 

 boiled, either by heating them with a little alkali on silver foil (when a 

 yellowishbrown spot of sulphide of silver will be formed,) or by boil- 

 ing their alkaline solution for some time with strong acids, when sul- 

 phuretted hydrogen will be developed, or with acetate of lead, when 

 sulphide of lead will be precipitated. It is, however, worthy of notice 

 that the protein-compounds may contain sulphur under conditions in 

 which its presence cannot be detected, as Mulder has shown, by the 

 ordinary tests. These were the bodies which were at one time re- 

 garded by Mulder as protein, or the non-sulphurous constituents of 

 albuminous matters, but he has subsequently discovered* that the 

 substance formerly termed protein contains sulphur. On treating 

 albuminous substances with a dilute solution of potash as pre- 

 scribed for the preparation of this supposed protein, they lose the 

 property of indicating the presence of sulphur by the ordinary 

 tests. Mulder endeavours to explain this phenomenon by suppos- 

 ing that those compounds which yield a sulphur-reaction, con- 

 tain sulphur combined with amide, and therefore as sulphamide 

 H 2 NS ; and further, that on treating them with potash, 2 atoms 

 of sulphamide by assimilating 2 atoms of water, are decom- 

 posed into ammonia which escapes, and also into hyposulphurous 

 acid, which combines with the non-sulphurous atomic group 

 to form those compounds which yield no sulphur-reaction 

 on silver foil. It certainly is true that all these compounds on 

 being digested with caustic fixed alkalies, develope ammonia, and 

 that those yielding the sulphur-reaction contain more nitrogen 

 than those which do not exhibit it. The assumption of the 

 presence of sulphamide in these substances, must, however, still 

 be regarded as a somewhat hazardous hypothesis, in the first place, 

 because we are as yet wholly unacquainted with this sulphamide, 

 whether in an isolated or combined state; secondly, because a 

 combination of hyposulphurous acid with an organic, scarcely basic 

 substance, is as unlocked for a phenomenon, as that it should not 

 be separable by stronger acids from its combination with the protein ; 

 * Chem. Untersuch. ubers. v. Volcker. H. 2, S. 179-272. 



