Il6 NUTRITION AND METABOLISM. 



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Hydroxy-phenyl-acetic acid Cresol 



The formation of hydrogen, methane, and nitrogen is not as easily 

 explained and probably means a more complicated change of the molecule 

 than a simple hydrolysis. 



Many protein compounds contain, besides the organic elements, 

 carbon, oxygen, hydrogen and nitrogen, larger or smaller amounts of 

 phosphorus and sulphur. The phosphorus compounds may be changed 

 to phosphine (PH 3 ), which is a gas of a strong disagreeable garlic odor. 

 Generally, however, the phosphorus of protein after its degradation is 

 found as phosphoric acid (H 3 PO 4 ). Very little is known about the 

 phosphorus of organic compounds and the changes it may undergo in 

 the putrefaction process. 



The sulphur of proteins is commonly changed to hydrogen sulphide 

 (H 2 S) . This may be the result of a hydrolytic cleavage or of a reducing 

 process. Some microorganisms are able to form mercaptan (CH 3 SH), 

 a compound of very foul penetrating odor. 



The production of all these compounds may take place under strictly 

 anaerobic conditions. Hydrolysis and intramolecular rearrangements 

 of the atoms within the molecule suffice to account for these changes. 

 The products of this anaerobic decomposition are mainly ammonia, 

 amins, amino-acids, alcohols (phenol), acids (acetic, butyric, capronic), 

 hydroxy-acids, phosphoric acid, hydrogen sulphide. Many micro- 

 biologists emphasize the distinction between the putrefaction as an 

 anaerobic process, and the decay as an aerobic process. The anaerobic 

 putrefaction produces offensive odors caused by indol, skatol, butyric 

 and capronic acids, amins, phenol, and hydrogen sulphide, while the 

 aerobic decay does not show such products. This distinction between 

 putrefaction and decay is an artificial one, however, and cannot always 

 be carried through. Facultative anaerobes will decompose proteins 

 in different ways with air and without, and in nature both processes 

 usually take place at once. It has been mentioned in the chapter on 

 oxygen requirements that many obligate anaerobes can grow exposed 

 to the air if at the same time some aerobic organisms develop in the same 

 medium. This is the case in most of the decompositions occurring in 

 soil, in the dead leaves of the forests, in manure piles, in spoiling foods. 



If oxygen has free admittance to the decomposing protein, the above 



