216 ORIGIN AND NATURE OF LIFE 



double life-cycle, in part consummated in man, 

 and in part in the insect. 



One of the most fatal of diseases, syphilis, 

 a most potent factor in racial degeneration, 

 which, unfortunately, flourishes in all climates, 

 has recently been shown to be a protozoan 

 disease carried by a minute animal organism 

 called, from its spirally arranged or twisted 

 form, a spirochete. 



Most classical descriptions of a typical 

 living cell are based on that particular class 

 of animal cell called an amoeboid cell, although 

 the word cell itself is derived from botany. 

 In plant tissues where growth is fairly rapid, 

 the cells lie close alongside of one another, 

 separated by outer membranes or cell walls, 

 so that the appearance comes to resemble the 

 cells of a honeycomb. 



The word cell, later came to be extended to 

 all living units as shown by the microscope, 

 although the wide and free exchanges of cells 

 with one another make the word rather a 

 misnomer, and the typical free unicellular 

 organism, as will be seen, is not at all described 

 by the word in its usual non-technical meaning. 



Amoeboid cells are found in sea and pond 

 water carrying on an independent existence, 

 and, in a dependent form as to nutriment, 

 in the blood and body fluid of higher animals, 



