A new micro-respirometer with automatic setting and recording apparatus.

The instrument was designed to measure the O2 uptake of living material which consumes between o-oi and 5-0 yl. O2/ hr. Its accuracy is +o-ooi /u.1., and it has the following advantages over other micro-respirometers of similar sensitivity. (a) It is robust, easy to handle and is suitable for routine use. (b) The respirometer constant is independent of the gas volume of the reaction vessel. (c) Its sensitivity is independent of the volume of the reaction vessel, and it can therefore be used with relatively large amounts of living material. (d) Experiments can be carried out over a wide range of temperatures without appreciably altering the accuracy. (e) It can be coupled to apparatus (described at the end of this paper), which automatically measures and records the rate of O2 uptake. A comprehensive review of the better known micro-respirometers has been given by Tobias (1943), but to facilitate comparison with the present instrument a list of the characteristics of some of them are given in Table 1.