44 HUMAN BIOLOGY 



organism, capable of synthesizing its own complex from 

 the carbon dioxide, nitrogen and other constituents of its 

 habitat, thus increasing in size, which would at length 

 entail divisional fragmentation and reproduction. So would 

 begin the long reign of life on earth. 



At what temperature of the primal surface water of the 

 earth this synthesis occurred can only be conjectured. It 

 must have been not above 8o°c., and possibly much lower, 

 for although certain algae live and multiply in the waters 

 of hot springs at temperatures above 8o°c., and bacteria 

 of the thermophilic class can be cultivated in media at 

 8o°c., with an optimum of 6^° to 70°c., this accommodation 

 to high temperatures may be a later adaptation. When, 

 of course, a living complex is formed of proteins of a simple 

 type it should, one may suppose, be more resistant to the 

 action of heat, but many of the proteins which we can 

 prepare from animal and vegetable cells are "denatured" 

 at 6o°c., and at 8o°c. all are so altered that the life of the 

 organisms yielding them or formed of them at once ceases. 

 Indeed there are few organisms, and these nearly all bacterial, 

 which can survive a temperature of 50°c. maintained for 

 several days. Possibly the protocyte, because of its com- 

 paratively simple constitution, may have been able to 

 survive, and even to thrive, at 8o°c., but as the temperature 

 of its media fell gradually it would adjust itself accordingly, 

 and thereby finally develop an altered protein complex 

 at 20° to 30°c., which at higher temperatures, 50° to 70°c., 

 would be "denatured," thus ceasing to live. In this adjust- 

 ment it is possible that new amino acids, those with cyclic 

 atom complexes in them for instance, would be formed 

 which, entering into the constitution of the protein complex, 

 made it more sensitive and more readily affected by higher 

 temperatures. 



To summarize: the primal organism, the protocyte, was 

 ultramicroscopic in size, was of comparatively simple 

 constitution, and began as a product of the union in a 

 special complex of a number of amino acids which were 

 formed from constituents of the atmosphere when the 

 condensations of water vapor, at or below ioo°c., were 

 continuous, and when also evaporation of small isolated 



