70 MOUNTING AND PREPARATION OF OBJECTS. 



The clove oil is removed from the section in the 

 same manner as the alcohol, and a drop or two of 

 damar placed upon it before its removal from the 

 spoon. When it becomes transparent, which gener- 

 ally takes place after the lapse of a few seconds, it is 

 floated on to the slide by the aid of a needle, and 

 finally mounted in the manner already described. 



The following method of staining with chloride of 

 gold has given more uniform and successful results, 

 when sections are required, than the original plan of 

 freezing the fresh tissue before staining. Place the 

 fresh tissue in one an a half per cent, solution of 

 bichromate of ammonia for fifteen to twenty days, 

 make sections in the ordinary way and dip them in 

 a solution of one part of double chloride of gold and 

 potassium in 10,000 of distilled water, wash in hy- 

 drochloric acid, 1 part in 2,000 of water, then place 

 them for ten minutes in hydrochloric acid one part, 

 and sixty per cent, solution of alcohol 1,000 parts, 

 clear with oil of cloves and put up in damar or bal- 

 sam in the usual way. 



The discovery of bacteria in diseased tissue, and 

 the probability that a special form accompanies each 

 disease, has excited considerable interest in the 

 labours of Elrich, Koch, and others, who have in- 

 vestigated the subject, and to whom we are in- 

 debted for the methods of rendering the organisms 

 visible. 



The following is a modification of the method 

 adopted for demonstrating the presence of the 



