COLLODION AND OTHER IMBEDDING METHODS. 12 



out with the mass after hardening, and cut with it. The 

 edges of the gelatin form good orientation lines. 



HALLE and BORN (see Zeit. f. u-iss. Mile., xii, 3, 1896, 

 p. 364) use plates of hardened white of egg, in which a 

 shallow furrow for the reception of the objects has been cut 

 by means of a special instrument. See further under 

 Enibryological Methods Reconstruction. 



156. Hardening, Preliminary. This is logically the next 

 step, but as a matter of fact is frequently begun before. 

 For the different processes of the collodion method so run 

 into one another that it is difficult to assign natural lines of 

 demarcation between them. 



The objects being imbedded, and in the stage at which we 

 left them at the end of 155, the treatment should be as 

 follows : The receptacles or supports are set with the mass 

 under a glass shade allowing of just enough communication 

 with the air to set up a slow evaporation. Or porcelain 

 moulds or small dishes may be covered with a lightly-fitting 

 cover. As soon as the added thick collodion (of which only 

 just enough to cover the object should have been taken) has 

 so far sunk down that the object begins to lie dry, fresh 

 thick solution is added, and the whole is left as before. (If 

 the first layer of collodion has become too dry, it should be 

 moistened with a drop of ether before adding the fresh 

 collodion) . Provision should be again made for slow evapora- 

 tion, either in one of the ways above indicated, or, which is 

 perhaps better, by setting the objects under an hermetically 

 fitting bell-jar, which is lifted for a few seconds only once or 

 twice a day. I have sometimes found it advantageous to 

 set the objects under a bell-jar together with a dish con- 

 taining alcohol, so that the evaporation is gone through in 

 an atmosphere of alcohol. This is especially indicated for 

 very large objects. The whole process of adding fresh col- 

 lodion, and placing the objects under the required conditions 

 of evaporation, is repeated every few hours for, if need be, 

 two or three days. 



V 



When the mass has attained a consistency such that the 

 ball of a finger (not the nail) 110 longer leaves an impress on 

 it, it should be scooped out of the dish or mould, or have the 

 paper removed if it has been imbedded in paper, and be 



