564 



APPENDIX 



areas (figure 91). For this reason a batch-type washing machine is not desirable 

 because the cleaned equipment must be removed at the same point at which it was 

 inserted when it was dirty. The most feasible design is one incorporating a continuous 

 chain passing through a tunnel in which jets of water under high pressure are used to 

 clean the equipment. In machines of this type there should be at least three stages, 

 (1) a rinse with cold water to remove most of the soiled material, (2) a spray of hot 

 water containing detergent or other washing compound, and (3) a very hot (sterilizing 

 temperature, if possible) rinse at the clean end. The length of the tunnel, the speed of 

 the conveyor, the type of cleansing chemical, water pressure from jets, number of jets, 

 and the temperature of the water determine the effectiveness of the cleansing. 



Fig. 91. Clean equipment assembly area. 



Note washing machines mounted through walls separating clean and dirty areas. 



The air pressure in the washing areas should be high on the clean side and low 

 on the dirty side. Precautions must be taken to insure maintenance of pressure despite 

 the loss of air through the tunnel of the washing machine. Curtains over the ends of 

 the tunnel can be helpful in this respect. 



Washing machines should be equipped with an exhaust system to remove excess 

 water vapor, thermostatic controls to shut off the machine if the water temperature 

 drops below the desired level, and safety devices to stop the conveyor if equipment 

 becomes jammed in the machine. 



PROCUREMENT 



The usual method of obtaining mice for experimental purposes is by purchase from 

 commercial breeders. A good list of these breeders in the United States is available 

 from the Institute of Laboratory Animal Resources. Since this is an excellent source of 

 such information to list them again is superfluous ; it is more important to discuss methods 

 of selecting from the sources listed. 



