LABORATORY STUDIES AND DEMOXSTRATIOSS. 2*25 



the ribbon- method,'^ the knife being "kept dry in eitlier cai^e. In 

 mounting they should be lixed by tlie culludiun-niethod. (^Seo 

 Collodion and Clove-oil.) 



B. Celloidln MdluxJ. — This is especially ap])licable to <k'li- 

 cate ve<>:etal tissues. After deli vd rat iu*^ the obifc-t thomuirldv in 

 alcohol, soak it 24 hours in a mixture of ecpial parts of alcohol 

 and ether. Make a thick solution of celloidin in the same mix* 

 ture and soak the object for some hours in it. It may then ho 

 imbedded as follows: Dip the smaller end of a tapering (M»rk 

 in the celloidin solution, allow it to dry for a monieiit (hh»wing 

 on it if necessary), and then build upon it a mass of celloidin, 

 allowing it to dry a moment after each additi<»n. Transfer the 

 object to the cork and cover it thoroughly with the celloidin. 

 Then float the cork in 82-85^ (0.842 sp. gr.) alcohol until the 

 mass has a firm consistency (24 h.). It may then be cut in the 

 microtome with the oblique knife, which nnist be kept dripping 

 with 82-85,^ alcohol. Keep the sections in 82-85^ alcohol until 

 ready to mount them, then soak them for a minute in strong 

 alcohol, transfer to a slide, pour on chloroform until the alcohol 

 is removed, drain off the liquid, quickly add a drop of balsam, 

 and cover. (See also Whitman, 1. c, p. 113.) 



* See Whitman, 1. c. p. 71. 



