He terms "sterile" and "pure" can be used interchangeably when discussing cultures, because they both refer to a culture that has not been contaminated.

In  microbiology, pure culture is a laboratory  culture  containing a single  species  of organism. it is usually derived from a mixed culture. pure culture transfers a small sample into new, sterile  growth medium  in order  to distribute the individual cells across the medium surface. it separates the individual cells. when the cells multiply, each will form a colony and it then may  be used to inoculate more medium. 

Was giving by lincoln on march 4, 1865-as lincoln prepared to speak, the civil war was drawing to a close-lincolns address of 703 words was the second shortest inaugural address-lincoln mentions god 14 times-505 of the words were one syllable -he used the word "war" or it's pronoun 9 times