div class=ts-pagebutton class=gotoPage data-page=1Page 1button div class=ts-imageimg data-url=a-colony-of-specific-pathogen-free-ratshtmlpage=1 data-page=1 class=ts-thumb lazyload alt=Page 1: A Colony of Specific Pathogen-Free Rats loading=lazy src=data:imagegifbase64iVBORw0KGgoAAAANSUhEUgAAAAIAAAACCAQAAADYv8WvAAAAD0lEQVR42mP8X8AwAgiABKBAv+vAXklAAAAAElFTkSuQmCC data-src=https:reader035vdocumentssitereader035viewer2022080321575068271a28ab0f07aed6d5html5thumbnails1jpg width=140 height=200 divp© 1964 Nature Publishing Grouppdivdiv class=ts-pagebutton class=gotoPage data-page=2Page 2button div class=ts-imageimg data-url=a-colony-of-specific-pathogen-free-ratshtmlpage=2 data-page=2 class=ts-thumb lazyload alt=Page 2: A Colony of Specific Pathogen-Free Rats loading=lazy src=data:imagegifbase64iVBORw0KGgoAAAANSUhEUgAAAAIAAAACCAQAAADYv8WvAAAAD0lEQVR42mP8X8AwAgiABKBAv+vAXklAAAAAElFTkSuQmCC data-src=https:reader035vdocumentssitereader035viewer2022080321575068271a28ab0f07aed6d5html5thumbnails2jpg width=140 height=200 divp© 1964 Nature Publishing Grouppdiv