2 DISSECTION AND DRAWING 



II. ON DISSECTION. 



The object of dissection is to separate the several parts and 

 organs from one another, so as to define their boundaries and 

 display clearly their mutual relations. Dissection consists 

 mainly in removing the " connective tissue " which binds the 

 several parts together. 



The following rules should be carefully attended to : 



1. Pin down the animal firmly to the dissecting board. 

 Never attempt to dissect a specimen that is not so fixed. 



2. In pinning out a dissection 'stick the pins in, not vertically, 

 but obliquely, so that their heads do not get in the way or 

 obscure the dissection. 



3. Never cut away anything until you are quite certain what 

 it is you are removing. 



4. Put the part you are dissecting slightly on the stretch ; 

 e.g., when dissecting the bloodvessels or nerves of the throat, 

 distend it by passing a small roll of paper or lumps of cotton- 

 wool down the oesophagus ; or when dissecting the muscles of 

 the leg, pin out the leg in such a position as to stretch the 

 muscles you are cleaning. 



5. In cleaning bloodvessels or nerves always dissect along 

 them, and not across them ; and avoid laying hold of them 

 with the forceps. Similarly when cleaning muscles, dissect 

 along their fibres and not across them. 



6 . Fine dissections should be done under water, which sup- 

 ports the parts and greatly facilitates the operation. A stream 

 of water allowed to play gently on the dissection from time to 

 time is often a valuable aid. 



7. The dissection of muscles, and still more of nerves, is 

 greatly aided by placing the specimens in spirit for a day before 

 dissecting. 



8. Keep your instruments clean and sharp. Be careful not 

 to blunt your fine scissors OF scalpel by using them for cutting 

 hard parts. 



9. If you get in a muddle, stop and wash the dissection 

 thoroughly under the tap before proceeding further. 



III. ON DRAWING. 



It is absolutely essential to draw your dissections, and this 

 must on no account be omitted. Keep a separate book for 



