O THE FROG 



III. GENERAL DIRECTIONS FOR DISSECTING. 



1. Keep all necessary instruments on the table before you 

 where they can be found without loss of time. 



2. Scalpels should be kept sharp. A whetstone is pro- 

 vided and students will be instructed how to use it. 



3. Instruments should be used only for the purposes in- 

 tended. Fine scissors and forceps are delicate instruments 

 and will not stand rough usage. 



4. Each student should provide a towel for individual 

 use, also a soft cloth (a worn handkerchief is excellent) for 

 drying cover slips. 



5. In the description of. animals possessing bilateral sym- 

 metry, the terms right and left refer to the right and left 

 sides of the animal, not of the observer. The term dorsal 

 means the side that is ordinarily uppermost during life; 

 ventral means the side that is ordinarily kept toward the 

 earth. The anterior end of the body is the one pointing in 

 the direction in which the animal ordinarily moves (i. e., the 

 head end), as opposed to the posterior end. Medial is used 

 to indicate nearness to the median line; lateral is the con- 

 trasting term. Proximal refers to that part of an organ or 

 structure nearest to its center or to its attachment to the 

 body; distal is the opposite adjective. 



6. If the specimen is being preserved in formalin, always 

 wash it thoroughly in water before beginning work. Ordi- 

 narily this will not be necessary, since the formalin-preserved 

 material is usually rinsed in water and placed in alcohol be- 

 fore being furnished to classes. 



7. The specimen should ordinarily be kept in a dissecting 

 tray while being dissected. In the case of animals as large 

 as the vertebrates, it is usually better not to pin the specimen 



