352 MANIPULATION. 



CHAPTER XIV. 



METHOD OF DISSECTING VEGETABLE AND ANIMAL TISSUES. 



Vegetables. — The process of dissecting vegetable tissues is 

 much more easy and less complicated than that of animals, 

 the chief operation in the former being the separation of the 

 woody and vascular parts from the investing cellular ones; 

 this is effected by the combined operations of macerating and 

 tearing, little (if any) absolute cutting being required. 



For the purpose of dissecting spiral vessels, and particular 

 kinds of woody fibres, either of the simple microscopes before 

 mentioned will suiEce ; of these, perhaps, that of Mr. Slack, 

 described at page 57, will be the best ; but that of Mr. Powell, 

 figured at page 52, or those of Mr. Eoss, at pages 59 and 61, 

 when provided with the arm rests, wiU be found nearly as 

 convenient. A good idea of the structure of a plant may be 

 known by sections made in various parts and directions by 

 the machine described at page .336 ; but the individual cells 

 or vessels must be dissected away from the enveloping tissues 

 before their true nature can be properly understood. The 

 process consists of making these tissues very soft by macera- 

 tion, in order that they may easily be separated from others 

 that are more durable ; the maceration should be carried on in 

 water, which, for the purpose, should not be changed (however 

 offensive it may become) until the parts dissected are clean 

 enough to be mounted, as the addition of fresh water wUI 

 retard the macerating process. Supposing the objects lo be 

 dissected out to be spiral or other vessels, and that by mace- 

 ration the surrounding parts are soft, a portion containing 

 the vessels must be laid either in a glass trough, or on -a o-lass 

 Avith some water, and placed upon the stage of the microscope, 

 one part being held with the forceps, whilst another pair of 

 forceps, or a dissecting needle, is employed to separate all the 

 cellular tissue from the vessels ; sometimes two of the needles 

 may be used for the purpose instead of the forceps. As soon 



