DISSECTION OF VEGETABLE MATTER. 



179 



shell, g the spittle glands, th the throat, s the stomach, r the 



odontophore, br the breathing gills, a anus, and o the ovary 



carrying eggs. 



The next illustration shows an oyster lying in its shell 



(Fig. 167) ; m is the lower half of the mantle, wt a piece of 



upper half, g the breathing gills, 

 h the heart, Iv the liver, Ip the 

 lips, o the opening of the mouth, 

 a the anus, ms muscle holding 

 shells together, and c elastic 

 cushion keeping shells apart. 



FIG. 166. 



Dissection of vegetable matter is usually preceded by pro- 

 longed immersion in water, in order to soften the parts to 

 be separated ; but very often indeed the tissues withstand 

 this action, and so recourse is had to various other solu- 

 tions which are found necessary. Caustic soda in dilute 

 solution is a favourite reagent for the differentiation of 

 vegetable matter. It is the solution used by the paper- 

 maker for the disintegration of the leaf of esparto grass, 

 the fibres of which furnish him with a valuable paper-making 

 material. 



Fibro-cellular tissue may be conveniently studied in the 



N 2 



