Humphry Davy Rolleston, Dictionary of National Biography… (1912)
“ Macfadyen's main bacteriological work was on the intracellular juices or endotoxins of certain bacteria. While some germs such as those which produce diphtheria and tetanus give off poisons as they grow, others, such as those responsible for cholera and typhoid fever, retain their poisons, which are therefore known as endotoxins. In order to obtain these endotoxins Macfadyen froze bacteria by means of Sir James Dewar's liquid air to a temperature of - 190° C, and then ground up the bacteria thus rendered brittle. ”
