122 ANATOillCAL TECBKOLOQY. 



these cases, however, if the scope of the final preparation is deter- 

 mined, most of the parts not involved may be removed at once, thus 

 saving alcohol or storage room, and — if the specimen is fresh — insur- 

 ing the more complete access of the alcohol. This measure is par- 

 ticularly important in the case of viscera or massive muscular organs, 

 and especially the brain of large animals and man. Even vpith the 

 brain of the cat, if the aulic region, for instance, is to be examined, 

 it is well to remove the dorsal and lateral parts of the hemispheres. 



§ 291. Deterioration of Alcohol. — During its use upon speci- 

 mens, alcohol is subject to four kinds of deterioration : — 



It may become colored by solution of coloring matters ; turhid 

 from the suspension of small particles ; offensive from the solution 

 of malodorous matters ; and weaJc from the evaporation of the 

 pure alcohol, the impartation of alcohol to the specimen, the ab- 

 straction of water from the specimen, and the absorption of mois- 

 ture from the atmosphere. 



§ 292. Puriflcation. — Aside from distillation for the sake of 

 strengthening, alcohol may be purified and improved in three ways : 

 settling ; filtration for clearing ; filtration for deodorizing. 



% 293. Settling. — Let the alcohol stand for a few hours undis- 

 turbed. Place a second jar close to it, so that the first need not be 

 carried, and pour the alcohol into it very carefully, and without 

 reversing the tilt until the dregs begin to approach the mouth. If 

 the alcohol is less than 20 per cent., or if the dregs are very foul, 

 they should be thrown away. But usually the dregs should be 

 poured into a more slender jar, and allowed to settle a second time. 



§ 294. Filtration for Clearing. — When alcohol is simply some- 

 what turbid, as usually is the case after the settling, or if its in- 

 tended use does not require deodorizing, the following process is 

 sufficient : Push some cotton into the narrow part of a large tunnel, 

 set the tunnel into a jar, and cover it closely. According to the 

 compactness of the cotton will the alcohol filter through more or 

 less rapidly, and with greater or less change of color and clearness. 

 The same cotton should not be used a second time. 



A. Clearing may be effected at the same time with deodorizing', if the perforated lid 

 of the filter to he described is covered with muslin, and if one or more layers of muslin 

 are so placed that the alcohol must pass through them before reaching the animal charcoal. 



B. During the filtration of alcohol, unless it is conducted into a receiver with a mouth 

 just large enough to receive the discharging end of the funnel, or the tube connected 

 therewith, let these pass through a hole in a metal, wooden, or pasteboard cover of 

 the jar. 



