108 THE MICROSCOPE. 



the story of the celebrated tunnel escape of February 9, 1864, 

 never fails to interest the visitors. One hundred and nine 

 Union officers made their escape through that tunnel, which 

 formed one of the most thrilling events in the history of the 

 war. 



QUESTIONS ANSWERED. 



Note.— Dr. S. G. Shanks, of Albany, N. Y., kindly consents to receive all sorts of ques- 

 tions relating to microscopy, whether asked by professionals or amateurs. Persons of ah 

 fades of experience , from the beginner upward, are tvelcome to the benefits of this depart- 

 ment. The questions are numbered for future reference. 



161. Give in detail the best way to imbed pathological and biological 

 material in celloidine, so one can follow each stage. How may I 

 overcome the "giving" of the material so as to get thin and uniform 

 sections ?—E. F. H. 



Minot's method contains all the essentials. Make two solu- 

 tions of celloidine in a mixture of equal parts of absolute alco- 

 hol and ether. A thin syrupy solution for infiltrating the 

 tissue, and a thick molasses-like solution for the proper imbed- 

 ding medium. The tissue, properly hardened and dehydrated 

 iD alcohol, is placed in a mixture of equal parts of absolute 

 alcohol and ether for 24 hours, then directly into the thinner 

 celloidine solution for one to three days, according to the size 

 and firmness of the specimen. Cut a flat top cork to a size to 

 accommodate the specimen, wrap a piece of filter paper around 

 it and fasten together with pins, the whole forming a sort of a 

 box with a cork bottom. Wet the cork bottom with absolute 

 alcohol, drop in some of the thick celloidine. When somewhat 

 hardened, arrange the specimen in place. When firm enough 

 to stand, fill the box with the thick celloidine so that it will 

 cover the specimen about half an inch deep. The solution 

 shrinks considerably in hardening. Allow the box and con- 

 tents to stand until firm enough to hold together. A piece of 

 lead with a pin through it may be stuck to the lower side of 

 the cork so the whole will sink right side up, then drop it into 

 70 or 80 per cent alcohol. After one to three days the celloi- 

 dine will be hard enough for cutting. Strip off the paper and 



