128 RADIOISOTOPES IN BIOLOGY AND AGRICULTURE 



bottle fastened to the outside of the cage and fitted with a rubber stopper 

 through which passes a glass tube with a fire-pohshed opening of about 

 3 mm at the licking end ; this is extended into the cage so that the rat may 

 conveniently reach it. Aluminum tubes are often used to avoid the high 

 breakage of glass, and large-size water bottles have been found easier to 

 clean and also to require less frequent filling. 



Cages are customarily washed once every 2 or 3 weeks. They are 

 usually soaked in hot water containing soaps or detergents, followed by 

 hand scrubbing, washing, and air-drying. Steam sterilization or a 2 per 

 cent cresol dip is often employed. The possibility of infection may be 

 reduced by the following practices: sterilization of bedding and litter, 

 exclusion of wild mice and rats from the colony, vermin and insect control 

 with insecticides, and the quarantining of animals before their introduc- 

 tion into the colony. 



Brief mention is made of facilities required for the domestic fowl, which 

 is becoming increasingly important as an experimental subject (12, 13). 

 Chicks are inexpensive and can be obtained in large numbers with reason- 

 able uniformity at any season of the year. For embryological studies, 

 fertile eggs can be obtained from commercial hatcheries and incubated in 

 small cabinet-type incubators. These hold about 500 eggs and are avail- 

 able commercially at reasonable cost. Electric brooders can be pur- 

 chased which are quite suitable for laboratory use. The main points 

 are that there should be space for the chicks away from the heated com- 

 partment and that the unit may be easily cleaned. To avoid problems 

 that may result from the chicks' eating their excreta, it is advisable to use 

 screen floors; 3'^-in. mesh is suitable for young chicks, and coarser screens 

 as the birds get larger. Up to 50 chicks can be placed in the 6 to 8 ft- of 

 the usual brooder compartment. The chicks are kept at 90 to 95°F 

 during the first week and then at about 85°F with gradual reduction. At 

 3 to 5 weeks it will be necessary to reduce the number of birds per com- 

 partment by about one-half. From 6 to 12 weeks they can be kept in a 

 broiler battery at a temperature not below 60°F. Thereafter the birds 

 should be placed in individual laying cages. In general, excellent com- 

 mercial equipment and feed are available. Sanitation is not a partic- 

 ularly difficult problem; with most arrangements the droppings can be 

 collected on paper for convenient disposition. The dustiness of the feed 

 may become a hazard and require special precautions if radioactive mate- 

 rials are incorporated in the feed. 



Table 4-1 summarizes some approximate housing and management 

 requirements for the various laboratory animals. The values given are 

 representative of typical conditions and of course may be varied widely 

 depending on the size of the animal to be maintained, the number of 



