HANDLING OF EADIOISOTOPES WITH ANIMALS AND PLANTS 127 



agement practice is presented, since the data may be helpful in the estima- 

 tion of space requirements. The use of ra(hoisotopes imposes additional 

 needs for the avoidance of cross-contamination of animals and the elim- 

 ination of radioactive dust hazards from diets, shed hair, dried excreta, 

 and bedding. 



General Specifications. The following discussion applies primarily to 

 the laboratory rodent: Animal-colony rooms should have surfaces that 

 are verminproof and easily cleaned. Hard tile, glass bricks, or gloss- 

 painted surfaces are suitable for the walls, and concrete floors are satis- 

 factory, especiall}^ if sealed with suitable paint. Floor drains may 

 become a source of vermin and are therefore not usually recommended. 

 Incandescent lamps are generally used for lighting, which may be critical 

 in certain types of nutritional studies. Temperature control is generallj^ 

 required, at least to an extent that will avoid sudden changes. It is also 

 desirable that the humidity be controlled if practicable. If the studies 

 are such that the animals become experimentally valuable, it may be wise 

 to have an auxiliary source of heat for emergency use. The ventilating 

 system should be designed so that the animals are not exposed to direct 

 drafts. 



Simple rectangular cages of wire mesh mounted on movable racks are 

 widely used. A popular design is a drawer-type cage supported from 

 runners placed on the underside of a solid shelf which forms the top of the 

 cage. The excreta and spilled food fall through the mesh floor onto a 

 catch pan placed so that the animal cannot touch any of the material col- 

 lected in it. Sheets of waxed kraft paper or similar paper may conven- 

 iently be used for the collection of fecal material. Cages are generally 

 constructed of galvanized iron Avire and sheet metal. Stainless steel is 

 more durable and easier to clean but is considerably more expensive. 

 Wooden or plastic cages are well liked for mice. All cage equipment in 

 the nonradioactive area should be interchangeable, but not with that 

 coming in contact with radioisotopes. 



General Management. It is helpful to have one or two substantial 

 tables available. These are used for handling animals while administer- 

 ing the radioactivity or collecting blood samples. Also they can hold the 

 scales for weighing the animals. Reasonably accurate weights can be 

 obtained using a scale of about 1000 g capacity. Often it is very handy 

 to have a table mounted on casters so that it can be moved to service 

 colony cages or metabolism cages that are themselves not movable. 



For routine maintenance of the colony, pelleted commercial diets are 

 adequate, and several days' supply may be made available at one time, 

 thus reducing labor. Feed cups about 4 in. in diameter and 3 in. deep or 

 open mesh hoppers should be used in preference to dropping the food on 

 the bottom of the cage. Animals are usually watered from an imerted 



