400 Pierre A. Fish 



parts may be stuck together with mucilage aud after shellac- 

 ing again the specimen will be as durable as ever. 



There are objections to both the dry and glycerin methods. 

 The former renders the specimens too hard and there is per- 

 haps a little more shinkage ; with the latter there is more 

 flexibility but there is a greasy and disagreeable feel to the 

 preparations. Experiments are in progress with a view 

 toward combining the more desirable features of each, by 

 compounding an emulsion in the following proportions : 



Glycerin . . ' loo c. c. 



Castor oil loo c. c. 



Gum arable 50 grams 



or, 

 Gum tragacanth 50 grams 



If well made it does not "crack" and seems to penetrate the 

 tissues quite well though somewhat slowly. The emulsion 

 can be used repeatedly by rubbing it up again in a mortar be- 

 fore putting a new specimen into it. The brain may be shell- 

 aced as in the previous method. 



The writer wishes to acknowledge his obligations to Pro- 

 fessor Wilder whose kindly interest in this line of work has 

 rendered practicable many interesting experiments and whose 

 indefatigable energy in scientific research has been an example 

 as well as an incentive in the preparation of this paper. 

 Acknowledgments are also due to Professor H. H. 

 Donaldson of Chicago University and to Professor S. H. 

 Gage of Cornell for valuable suggestions. 



ithaca, n. y. 

 August, 1893. 



