Koch succeeded in staining the tubercle bacilli after long soaking of cover-slip preparations in alkaline methylene-blue and then using vesuvin as a brown contrast stain. Ehrlich first stained for fifteen to twenty minutes with an aqueous solution of aniline methyl violet or fuchsin, and then decolorised with dilute nitric acid, which eliminated the colour from everything except the tubercle bacilli. Other methods have been since devised, of which the following is the most convenient, especially for the examination of suspected sputum. For more complete study of the biological relations of the tubercle bacillus it is necessary to cultivate it on or in artificial media in the laboratory. The resistance to desiccation shown by the tubercle bacillus is its most significant biological feature. The best temperature for the growth of the mammalian tubercle bacillus is 37-38ºC. Cadeac and Malet have produced positive results by inoculation of material from tuberculous lungs which had previously been buried for 167 days.