332 THE BEGINNINGS OF LIFE. 



There are, indeed, weighty reasons why such a fluid 

 as the blood should not, amongst very highly organised 

 creatures, easily give birth to heterogenetic products 

 during the life of the individual. It is not a mere 

 excretion like the milk, but the most nearly vitalised 

 of all the fluids of the body, and subject to constant 

 changes from moment to moment in all the tissues: 

 so that, as long as the organism lives, the united mole- 

 cular activities of the various tissues are continually 

 influencing this all-pervading fluid, and tending to 

 maintain its ordinary characters x . But when death 

 is approaching, these united activities become weaker 

 and weaker, and changes may begin to take place 

 in the blood more closely resembling those which 

 occur in organic fluids out of the body 2 . It is quite 

 conceivable, also, that the changes which occur in the 

 blood in certain febrile diseases more especially when 

 they are associated with a very high temperature may 

 be of such a nature as to make the blood more than 

 usually prone to undergo rapid putrefactive changes 

 after death. And the occurrence of putrefactive changes 

 in animal fluids implies the presence of Bacteria. 



Facts can, indeed, be cited, tending to show that the 

 changes in the blood in these diseases do predispose it 

 to early putrefaction, and that the living organisms 



1 Seep. 1 88. 



2 It is quite certain that refuse fluids, such as urine in certain diseased 

 conditions, may contain an abundance of Bacteria and Torvla at the 

 moment when they are passed from the body. 



