PRESERVATION OF OSSEOUS AND HORNY TISSUES. 



By F. L. J. BOETTCHER, 



Of Washington, District of Columbia. 



INTRODUCTION. 



During the winter of 1909-10 the large collection of hippopotamus 

 skulls made by the Smithsonian African Expedition, under the 

 direction of Col. Theodore Roosevelt, in British East Africa brought 

 forcibly to notice the necessity of preventing the cracking, scaling, 

 and rupture (at times explosive) of tusks, which within a month or 

 two after their arrival often became badl}^ disfigured. 



Experiments for the accomplishment of the object soon showed 

 the possibihty of such a conservation. Acting upon the hypothesis 

 that expansion and contraction are principally due to absorption and 

 desiccation, a check to these, as complete as possible, seemed called 

 for, and experiments were consequently conducted in accordance with 

 such premises. 



Under normal conditions during the Ufe of the animal not even 

 the enamel of the teeth shows signs of scaling. One and the same 

 fluid permeates aU their tissues, however different in density, chemical 

 composition, and conductivity, forming one homogeneous unit, 

 homogeneous to the active and normal forces of expansion and 

 contraction. 



To preserve natural objects successfully it is necessary to imitate 

 the conservative forces of nature and meet their imperative demands. 

 We must restore the homogeneity lost by desiccation, and to do so 

 fuUy and permanently a medium must be found that vnW be suffi- 

 ciently fluid to enter the most delicate capillaries and also sufficiently 

 indestructible to resist normal chemical atmospheric changes, such 

 as are likely to be found in a museum. 



Various substances for this purpose have been considered. The 

 retention of fats and of animal matter in skulls and bones, for example; 

 the infiltration of oils, of glue, of shellac; but not one of these is satis- 

 factory when one comes to consider its resistance to chemical changes 

 or its ability to completely exclude the air. 



Proceedings U. S. National Museum, Vol. 41, No. 1879. 



697 



