58 Thp: Microscope, 



has recntly been thrown out as to whether the fungus or the 

 bacillus was the main agent in preparing dough for bread. 

 Katharine Golden has made careful experiments, and has found 

 that each separately is capable of acting on the dough ; and, 

 therefore, in an ordinary raising neither can claim exclusive 

 credit. 



WAVS • 

 AND MEANS 



A METHOD OF EMBEDDING DELICATE OBJECTS IN 



CELLOIDIN. 



FRANK S. ABY, PH. B. 



The object, properly fixed and hardened, is placed for twenty- 

 four hours in a mixture of equal parts of alcohol and ether. It 

 is then transferred to a thin syrupy solution of celloidin, made 

 by dissolving celloidin in a mixture of equal parts of alcohol 

 and ether. After remaining in this solution for about twenty- 

 four hours, the object is covered with a thicker solution of cel- 

 loidin and is allowed to remain in the same for about tw-enty- 

 four hours, when it is ready to embed on cork. 



When ready to embed the object, a small quantity of the cel- 

 loidin solution is spread on clean glass (a slide will answer the 

 purpose), and allowed to dry. Then another coat is applied and 

 allowed to dry. This affords a firm celloidin bed upon which the 

 object is placed and arranged, care being taken to place it in the 

 desired position as quickly as possible, before the celloidin begins 

 to harden. The whole is now covered with successive layers of 

 the celloidin solution, until a firm support is built up for the 

 object. When sufficiently dry, the celloidin is removed from 

 the glass by means of a sharp knife, and if necessary, a pair of 

 scissors is used to trim the bed to the proper size and form. It is 

 now ready to embed on cork. 



The top of a cork is coated with celloidin solution and allow- 

 ed to dry. This is done to prevent air from rising from the cork 

 and forming bubbles in the celloidin. The object, in its matrix 



