Abstract
Many types of apparatus have been described for determining basal metabolism of small animals (1-4), especially the rat. Haldane's open circuit method(5), in which oxygen consumption and carbon dioxide production are determined simultaneously, has been widely used with various modifications. Most of such equipment has been designed for research purposes and is too complex and expensive for routine use in student laboratory experiments when several sets of the apparatus are required.
The device described in this paper is economical, simple to construct and operate, and quite accurate for equipment of its simplicity. About 30 pieces of this apparatus have been in routine use in our laboratory during the last 3 years with good results.
The apparatus is shown schematically in Fig. 1. A standard wide-mouth, half-gallon Mason jar is secured to a wood base by 2 wire straps. The glass liner is removed from a zinc top∗ and a 13 mm hole drilled in the center. A 5 ml burette is made by etching lines on an 11 mm o.d. glass tube with 1 mm walls. This burette is sealed in the jar top by slipping a 14 mm o.d. rubber tube over the burette and pushing this gasket into the hole in the zinc top. The animal container is fabricated from 6 mm mesh hardware cloth in the shape of a cylinder closed at one end. The approximate dimensions shown in Fig. 1 are suitable for the adult rat but the size of the animal container can be varied to fit smaller or larger animals.
To determine the oxygen consumption of a rat the bottom of the chamber is covered with 8 mesh soda lime. The rat is placed in the animal container and the open end closed with strips of 50 mm adhesive tape.
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