Fish, Formalin. 127 



may, after a week in the second solution, be removed to 50 per 

 cent., 70 per cent, and 90-95 per cent, alcohol for final storage. 



An objection to the use of the formalin solutions for mu- 

 seum purposes would be the large proportion of water present, 

 which would freeze at low temperatures and cause injury to the 

 specimen or jar containing it. Since formalin is readily miscible 

 with alcohol, as well as water, enough of the former might be 

 added to prevent the freezing, say equal parts of 95 per cent, 

 alcohol and i per cent, formalin ; the exact proportions have 

 not as yet been determined. 



After an immersion of two weeks in the formalin solutions, 

 a human brain lost only Q."^ per cent, of its weight; but after 

 an immersion in 50 per cent, alcohol for eight days and an im- 

 mersion for an equal length of time in 70 per cent, alcohol, a 

 total of sixteen days, it was found to have lost 22 per cent, of 

 its first weight. A monkey brain after an immersion of eight 

 days in the formalin mixture lost 5.4 per cent, of its weight; 

 continued immersion in the same fluid for eighteen days longer 

 caused a loss of less than 2 per cent. A fox brain was im- 

 mersed in a similar mixture for five days and lost 6.5 per cent, 

 of its weight ; it was left in the same mixture eighteen days 

 longer and lost 2.3 per cent, more of its weight. The brains 

 were firm and in excellent condition for dissection. 



The second, or i per cent, formalin solution redissolves any 

 of the sodium chloride that may remain in the brain, which is an 

 advantage if the specimen is to be treated with alcohol, as the 

 latter does not dissolve the salt. The brain should not be put 

 from the formalin solution immediately into the strong alcohol 

 as the tissue will shrink very materially. 



Brains hardened by the above mentioned methods do not 

 dry readily ; even alcoholic brains after soaking for a time in the 

 formalin solution do not dry quickly, which is a decided advan- 

 tage for class-room work. 



The preparation recently introduced undeir the name of 

 Formalose I have not yet had an opportunity to experiment with. 



The formalin hardened preparations are not so firm as those 



