=Advantages.= It is the cheapest and quickest method. It penetrates well and causes little contraction of the tissues, shortens the time in xylol and paraffin and makes more easy the cutting of dense fibrous structures. Cell-division figures are as well preserved as by alcohol fixation, and the staining of bacteria in the tissues can be carried out as well after acetone-fixation as after alcohol. It preserves lecithin, hence can be used for the fixation of nerve-tissues. When combined with formol (formol-acetone) the red blood-cells are well-preserved and take a brilliant eosin stain. =Disadvantages.= The disadvantages are practically the same as with alcohol fixation but not so marked. Fat is dissolved, cell-division figures are not so well-preserved as with mercuric chloride and Flemming’s solution, and the blood-cells not so well preserved as with formol and mercuric chloride. 2. =ALCOHOL.= Absolute, 95-96 per cent alcohol, or graded alcohols (70, 95 per cent. and absolute) may be used for fixation. For this purpose the stronger alcohols are preferable, as the weaker solutions do not fix quickly enough. On the whole the use of 95-96 per cent is to be advised. The pieces of tissue must not be thick. Plenty of alcohol should be used and it should be changed several times during the process of fixation, which for larger pieces requires several days. For the last change absolute should be used. Very small bits such as uterine curettings can be fixed in one hour, by using three changes of absolute alcohol. Since alcohol both fixes and hardens it has been generally used, but it is a relatively poor fixative. For after-hardening it is indispensable. Absolute alcohol may be made from 96 per cent by the use of fused copper sulphate. To test the strength of alcohol mix a few drops with pure water-free xylol; if no sediment appears when viewed against a dark background the alcohol is absolute or practically so. Many of the disadvantages of alcohol fixation can be obviated by the use of =formol-alcohol= (95 per cent alcohol 100 cc., formalin 10 cc.). =Advantages.= Cheapness, quickness, and ease of method. Can be used for quick diagnostic work. Penetrates well, and can be used for large pieces of tissue. Preserves glycogen, is especially good for the staining of bacteria in sections, and the majority of stains work well with alcohol-fixation. =Disadvantages.= Causes much shrinking and loss of finer details; preserves cell-division figures not at all or poorly; destroys the red blood cells; dissolves fat and other chemic products: does not permit of the use of certain specific staining methods (nerve-tissues); causes excessive hardness of fibrous and elastic tissues and makes cutting difficult.