130 



RADIOISOTOPES IN BIOLOGY AND AGRICULTURE 



occurred. They can then be replaced in the regular units, which will be 

 exposed to little or no contamination. To facilitate decontamination the 

 cages may be dipped in paraffin, or the flat metal surfaces can be coated 

 with strippable film. 



MICE, RATS, AND GUINEA PIGS. When quantitative separate collection 



of urine and feces is not required, home- 

 made racks and cages described as follows 

 have been found adequate: Hardware 

 cloth of about 3^-in. mesh is attached to 

 a wooden frame about 2 by 3 ft to form 

 the floor for six cages. The cages them- 

 selves are simply constructed from a single 

 length of M-in- hardware cloth to give a 

 cylinder about 10 in. in diameter and 7 in. 

 high. A 10-in. cake pan serves as a cover 

 and supports the water bottle. Feces and 

 urine pass through the wire mesh for collec- 

 tion and disposal. 



Numerous methods have been proposed 

 for quantitative separate collections of 

 feces and urine (15). A simple arrange- 

 ment that has been satisfactory for most 

 studies is illustratecf in Fig. 4-8. A com- 

 mercial rat-metabolism cage of 8-in. diam- 

 eter is used. The cage has a removable 

 wire-mesh bottom and brackets so that it 

 can be supported on a 9-in. -diameter 

 funnel. A small inverted funnel is sus- 

 pended by a wire from the center of the 

 cage bottom to direct the urine and feces 

 to the sides of the large supporting funnel. 

 The neck of the supporting funnel is cut 

 off at the base to provide a 1- to IH-i^- 

 opening. The separating unit is com- 

 prised of a 5-in. piece of 3-mm glass tubing 

 which has a 3- to 5-cm bulb at one end and 

 is drawn to a closed point at the other, a 15- to 30-ml centrifuge tube 

 which has indentations near the top to fit the neck of the bulb and keep 

 it centered, a block of wood with a hole to support the centrifuge 

 tube, and a 2-liter beaker. The unit is assembled as indicated in 

 Fig. 4-8, with the bulb centered about 5 mm beneath the large funnel 

 opening. In operation, the urine flows around the bulb into the centri- 

 fuge tube, and the feces strike the bulb and bounce into the beaker. All 



Fig. 4-8. Unit for quantitative 

 separate collection of feces and 

 urine from rats. A, wire-mesh 

 rat cage with removable bottom. 

 B, small funnel. C, large funnel 

 cut off to give li^-in. bottom 

 hole. D, two-liter beaker. E, 

 glass bulb with long stem. F, 

 centrifuge tube. G, wood block. 

 The urine flows down into the 

 centrifuge tube, and the feces 

 bounce off into the beaker. 



