[9] PRESERVATION OF MICROSCOPIC MATERIALS. 615 



preparations may be stained at once, and then treated with alcohol and 

 mounted iu balsam." 



The following directions for the preparation of the tongues of mam- 

 malia, for histological purposes, have been furnished by Mr. Edward B. 

 Poulton, of Oxford, England, in a letter to Prof. G. B. Goode, from 

 w^hich the following extract is taken : 



" It is well to cut out the organ, including the epiglottis. In the case 

 of rare animals that cannot be obtained fresh, a tongue preserved in 

 spirit is of great use, but is not so good as a chromic acid one of the 

 fresh organ. The best method of preparation seems to be the following : 

 Suspend the perfectly fresh tongue by a string in ^ per cent, solution of 

 chromic acid,* about a quart, to which one-half pint of methylated t spirit 

 has been added. (Three or four small tongues might be put in together; 

 a very large tongue would need more.) Leave iu this solution for a 

 week, and then change it, and after another week place the organ in a 

 pint of solution consisting of two parts water, one part methylated spirit 

 or alcohol, and after a few days or a week place in a pint of fluid con- 

 sisting of one-half water and one-half spirit; and theu,after a week,in one 

 pint of liquid consisting of two parts spirit and one part water, and then 

 in strong spirit, which need not be so much as one pint. In this a larger 

 specimen will keep any length of time, and is always ready for histologi- 

 cal work. Some tongues which I worked at, given me by Professor 

 Mosely, were iu beautiful condition, and had been hardened nine years 

 before. The first washes of spirit can be used many times for other 

 tongues, but it is best to have a series of labeled jars with the various 

 strengths of spirit (alcohol) in them, and pass the tongues from one into 

 the other, from the lowest to the highest grade of spirit. This saves ex- 

 pense, even though it may call for an extra change of strong spirit at 

 the end. The tongues should finally not cause the fluid to become yel- 

 low, but the first washes may be yellow (from the dissolved chromic 

 acid). The tongues can then be packed together in one jar in plenty of 

 strong spirit, each with a label tied to it, giving, if possible, the specific 

 and generic names and date. Thus many can be sent together. If you 

 ever get them, I should be very glad of spirit or fresh tongues (prepared 

 in chromic acid) of any Edentate, Marmoset, and any South American 

 monkey, tapir, peccary, or Solenodon. The chromic acid must not be 

 used again." This last remark applies in all cases to the use of chromic 

 acid. 



MerJceVs fluid. — Whitman gives the formula for the preparation of this 



as follows : 



Platinum chloride dissolved in water 1: 400 



Chromic acid dissolved in water 1: 400 



"Professor Merkel, who employed a mixture of these two solutions in 

 equal parts for the retina, states that he allowed from three to four days 



* If it cannot he ohtained fresh, it is still of great use to try the chromic acid up to 

 some days after death, but not in the ease of a regular spirit specimen, 

 t Alcohol will answer the same purpose. 



