Embedding Tissues and Section-Cutting 143 



hold the parts together ; now with a sharp knife cut off each 

 end of the bud so that the celloidin may easily penetrate to 

 the interior. Now place the specimen in equal parts of 

 absolute alcohol and ether for at least twelve hours. Then 

 transfer to the thin solution of celloidin, and soak until 

 completely infiltrated. Eemove and place in thick celloidin 

 for about twelve hours. Take out of celloidin on the point 

 of a needle, and hold exposed to the air for a few minutes, 

 to dry the celloidin around the exterior of the bud. When 

 dry, push gently off the needle into some methylated spirit, 

 and soak for at least twelve hours to complete the hardening 

 of celloidin. The specimen may then be embedded in 

 carrot, and the sections may be cut in any ordinary well 

 microtome. Worms must be cut up into pieces of about { 

 or ^ inch long ; these are then dehydrated in equal parts 

 of ether and alcohol, infiltrated with and embedded in 

 celloidin, and then treated in exactly the same way as 

 directed for flower-buds. 



When a number of celloidin masses are prepared for 

 future use, they must be preserved in a vessel of methy- 

 lated spirit. 



Embedding in Gelatine. — This method is very useful for 

 hairs, cotton, silk, wool, and all such fibres. Take, for 

 example, some human hairs about J an inch long, and make 

 a bundle of them ; tie them together either with a long hair 

 or with some fine cotton. Place the bundle in warm water 

 and soak for a few minutes. Now make up a strong 

 solution of some clear transparent gelatine. Cox's is very 

 good — say 1 ounce of gelatine to 6 of water. Transfer 

 the bundle of hair to this, place in a warm water bath, and 

 soak until the gelatine has penetrated all through the 

 bundle. Eemove from gelatine on the point of a needle, 

 and allow the mass to cool ; then place in methylated 

 spirit for about twelve hours. The embedded mass may 

 then be placed in a cylinder of carrot and transverse 

 sections cut in the ordinary well microtome. The sections 

 when cut are to be placed in strong spirit to dehydrate; 



