TH15 VICTORIAN NATURALIST. 17 



Microscopical Sociefy, for August, 1881 ^, wliich helped me out of 

 mj difficulty, arid gave "the one thing needful" to make mj last 

 experiment successful. It was to the effect that Professor Semper, 

 of Wurzburg, had recently exhibited to the Society there, some 

 zoological and anatomical preparations prepared by a new method 

 for dry preservation. Chromic acid and alcohol were used, and 

 the objects were steeped in oil of turpentine before drying. '• The 

 tissues whilst drying are permeated by innumerable small air bubbles, 

 and in consequence the preparations retain their original fi.rm 

 without sensible shrinking, whilst in colour they assume a white tint, 

 similar to that of a gypsum-model." 



On reading this, I was delighted. Eureka rose to my lips and 

 Tisions of success before my mind. A bath of oil of turpentine 

 solved the mystery, and completed the process before drying. 



And here you will observe that the process I have carried out is 

 not original. I have simply adopted a suggestion and achieved a 

 success. I understand that these dry preparations are made and 

 scld upon the Continent of Europe, although I have not as yet seen 

 any myself. The main object of this paper, however, as already 

 stated, is not to discuss the discovery, (for which there are several 

 candidates in the field, claiming the credit of having first made it 

 public), but to describe and explain the process, so that some of you 

 may be led to take it up and possibly improve upon it. 



There are just 3 re-agents required, each of wliich is used 

 separately — chromic acid for hardening, alcohol for withdrawing 

 water and excess of acid, and oil of turpentine to prevent shrinking 

 or drying. Simple as the process appears, it requires care and 

 attention in carrying it out. 



PcH-haps the most instructive way will be to take a small animal, 

 s^:ch as the Frog, and explain the various steps in connection with 

 it — the three stages of the preparation process. The exact time 

 will be given for each stage in thij specimen, (Frog), but you are to 

 bear in mind that this will vary according to size of specimen, 

 temperature, &c. It is an easy matter, liowever, to know when the 

 different re-agents have had their proper effect, and a. generrl 

 principle may be laid down. It can be felt when the specimen is 

 properly hardened, always remembering that too long immersion 

 makes it brittle. It can be seen when the alcohol has reistoved all 

 the water and excess of acid, for tlien the alcohol will I'emain clear 

 and without discolouration, and the final application of oil of 

 turpentine lias had its effect when any part on drying is whitish in 

 colour. 



To begin with, the Frog is opened up from the front, «o that tlio 

 hardening agent may have free access to all parts, for otherwise it 

 might not penetrate through the skin. Then it is pinned out on a 

 1. See also same Journal for October, 1882. 



