276 THE CIRCULATION OF NITROGEN [PART III 



such things as dead leaves, bark, resins, gums, &c., that excretions 

 or waste substances are eliminated. 



Sometime or other in the history of the organism, and in one 

 of many forms, the reproductive process begins. Animals form 

 eggs or buds, and plants form seeds, buds, &c. A minute portion 

 of the living substance — the immortal germ-plasm — is handed 

 down in some form or other as the offspring. From the point of 

 view of the race the reproductive act is the object of the life of 

 the individual, and being completed, death comes as a natural 

 consummation ; and the lifeless vesture, or body, is given over to 

 the forces of dissipation. The bacteria which inhabit the surfaces 

 of the body, and which during the life of the organism were 

 restrained by the vital activities of the latter, now become irres- 

 ponsible. Those processes which during life proceeded slowly and 

 orderly now go on rapidly, and are quite uncontrolled. Soon the 

 dead tissues of the plant or animal become resolved into a few 

 simple chemical substances, chiefly mineral dust, water and carbonic 

 acid gas. 



Putrefactive decomposition. Apart from the activity of putre- 

 factive and fermentation bacteria, no change, except the cessation of 

 the production of energy, and the reproduction of new organisms, 

 would take place upon the death of an organism. Even the pro- 

 teids of the animal body, the most unstable of chemical substances, 

 would persist unchanged for apparently an indefinite length of 

 time. It has been demonstrated that there are unaltered proteids 

 and fats in the substance of Egyptian mummies belonging to the 

 early prehistoric period (about 4000 B.c.)\ In the exceedingly dry 

 atmosphere of Eg}^t, and possibly because of the action of the 

 baths of common salt (which was the embalming substance em- 

 ployed), bacterial action is very largely arrested and putrefaction 

 does not occur. Extreme cold also inhibits the activity of pu- 

 trefactive micro-organisms, and so we have found the bodies of 

 mammoths, which probably lived prior to the time when the 



1 See Schmidt, " Chem. u. biol. Untersuch. von agyptischen Mumienmaterial," 

 Zeitschr. allgem. Physiol. Bd. vii. 2 and 3 Heft, 1907. It has been stated that 

 haemoglobin, the colouring matter of the blood, has been recognised; and even 

 that the proteids specific to the human body could be identified by serum 

 reactions. This, however, appears to be doubtful. 



