262 BACTERIA IN THE SEA [PART III 



result from the break-down of the proteid molecules. These are 

 very numerous and are still very complex chemical compounds. 

 A number of substances called amino-acids are produced, some of 

 which are leucine, tyrosine, glycine, &c. Albumoses and peptones, 

 very complex substances, may also be produced during the first 

 stages of these decompositions. Very malodorous substances such 

 as indol and skatol, substances to which the odour of the excreta 

 is due, are also produced. It is only during the last few years that 

 we have become intimately acquainted with the manner in which 

 the frightfully complicated proteid molecule-complex decomposes, 

 and the wonderful researches of Emil Fischer, Abderhalden and 

 others indicate that the actual manufacture of proteid substance in 

 the laboratory, with all the results that this achievement suggests, 

 may be a thing of the near future \ 



Now when putrefaction begins in a dead body much the same 

 series of compounds as are produced by the action of chemicals (in 

 the hydrolysis of the proteid) come into existence. The bacteria 

 seize on the dead substance and break it down. Some of the 

 putrefactive bacteria — the saprogenic species — break down the 

 proteid substance into simpler stuffs, and others — the saprophile 

 species — utilise these first products of decomposition as food. Both 

 processes go on together. Putrefaction is a very complex process 

 and it is modified by many agencies such as the temperature and 

 the presence or absence of oxygen. When oxygen is freely admit- 

 ted to the putrefying mass — aerobic putrefaction — rapid decompo- 

 sition with but little smell takes place. But when air is partially 

 or entirely excluded — anaerobic putrefaction — as in the interior of 

 a decomposing carcase, then foul-smelling products accumulate. 

 Sometimes ptomaines, many of them highly poisonous substances, 

 are formed. Altogether the putrefactive process is very complex, 

 and our knowledge of it is still very imperfect. 



But in the long run all putrefactive processes due to bacteria 

 have the same result. The complex proteid substance is broken 

 down into a few comparatively simple substances. These are 

 ammonia, carbon dioxide, sulphuretted hydrogen, water, phos- 

 phoretted hydrogen (which at once becomes oxidised by the oxygen 



^ An excellent account of these recent investigations is given by Plinamer in 

 Science Progress for July 1907. 



