92 PHYSIOLOGICAL ACTIVITIES 



to carbon dioxide or in the absence of oxygen partly to 

 marsh gas. 



The intermediate changes which the sulphur in proteins 

 undergoes are not known, but it is liberated as sulphuretted 

 hydrogen (H2S) or as various mercaptans (all foul-smelling), 

 or is partially oxidized to sulphuric acid. Some of the H2S 

 and the sulphur of the mercaptans are oxidized by the 

 sulphur bacteria to free sulphur and finally to sulphuric 

 acid. 



Phosphorus is present especially in the nucleoproteins 

 and nucleins. Just what the intermediate stages are, or 

 whether there are any, so far as the phosphorus is concerned, 

 in the splitting up of nucleic acid by bacterial action is not 

 determined. The phosphorus may occur as phosphoric acid 

 in such decompositions, or when the conditions are anaerobic 

 as phosphine (PH3), which burns spontaneously in the air 

 to phosphorus pentoxide (P2O5) and water.^ 



The hydrogen in proteins appears in the forms above 

 indicated: H4C, H3N, H3P, H2S, H2O and as free H. The 

 oxygen as CO2 and H2O. 



. In the breaking down of the complex protein molecule 

 even by a single kind of bacterium there is not a perfect 

 descending scale of complexity as might be supposed from 

 the statement that there result proteoses, peptones, poly- 

 peptids and amino-acids. These substances do result, but at 

 the time of their formation simpler ones are formed also, 

 even CO2, NH3 and H2S. It appears that the entire mole- 

 cule is shattered in such a way that less complex proteins 

 are formed from the major part, while a minor portion breaks 

 up completely to the simplest combinations possible. A 

 more complete knowledge of these decompositions will aid 

 in the further unravelling of the structure of proteins. The 

 presence or absence of free oxygen makes a difference in the 

 end-products, as has been indicated. There are bacteria 

 which oxidize the ammonia to nitric acid and the H2S to 

 sulphuric acid. (See Oxidation, Chapter XL) Bacteria 



1 It is probable that this is the way "Jack o'lanterns" or "Will o' the 

 wisps" are ignited. Marsh gas is produced as above outlined from the vege- 

 table and animal matter decomposing in swampy places under anaerobic 

 conditions and likewise phosphine. These escape into the air and the "spon- 

 taneous combusion" of the phosphine igtiites the marsh gas. 



