456 BIOLOGY OF THE LABORATORY MOUSE 



themselves may be of simple metal box- or pan-like construction with a 

 detachable screen lid permitting replacement of water bottles and food with- 

 out removal of the lid. Food and bedding are best stored in metal con- 

 tainers, bins, or special rooms protected from vermin and stray rodents. 

 Each cage as a unit should house the smallest number of mice consistent 

 with the total number and available space. Breeders are best kept in 

 separate cages in a separate room. 



Washing of the rooms, racks, and transfer of cages should be carried out 

 at least once a week. The attendant is best garbed in a coverall or gown 

 which can be laundered, and should scrub and dip his hands in disinfectant 

 between sections of racks while transferring animals from dirty to clean 

 cages. In a separate room the cages and water bottles are cleaned, washed, 

 and sterilized, preferably by steam. If chemical sterilization is employed, 

 a sufficiently long period of contact must be allowed to insure effective action 

 of the germicide. Sterilized wood shavings are most satisfactory for bed- 

 ding, and may be placed in the clean, dry cages before they are removed to 

 the animal room for the next cleaning. By following this cleaning technique, 

 dust in the animal room itself is reduced and disposal of waste becomes a 

 simple matter. 



A nutritionally complete diet may be prepared on the basis of the 

 McCollum or Steenbock formulas or their modifications (329, 321). Ade- 

 quate diets are also available commercially. Under ordinary circumstances, 

 sterilization of the food is not necessary. Except in special instances, little 

 can be accomplished by attempting to alter the specific host factors. 



Before being added to the general stock, new mice should be kept in 

 quarantine for at least 3 weeks, distributed in separate cages containing 4 to 

 6 mice each. Postmortem examinations, with cultures, should be made on 

 all dead animals. If infection is recognized, the cage-mates must be killed. 

 Should no cause for the death be found, the other animals in that cage are 

 watched for an additional 2 or 3 weeks. A second death is an indication for 

 destruction of the remaining animals in the unit; otherwise they may be 

 considered to be normal. 



Measures similar to quarantine should be taken in the event of an out- 

 break of disease in the general stock. At the first appearance of the disease 

 the room should be rigidly isolated and the diseased mice cared for only by 

 attendants who have no contact with normal animals. Depending on 

 previous conditions, the animals should be redistributed into the smallest 

 possible number per cage unit. A specific death is then an indication for 

 the destruction of all the mice in that unit. If the disease is very extensive, 



