ABSTRACT
For a variety of physiological and ecological reasons it is of importance to know the oxygen pressures at which the haemoglobins of different animals take up or part with oxygen. In the relatively few cases in which this has been studied in small animals, particularly invertebrates, the blood, since it is only available for investigation in very small amounts, has generally been considerably diluted with water. But the position of the oxygen dissociation curve of dilute haemoglobin is not necessarily the same as that in whole blood: the oxygen affinity may increase with dilution (Florkin et al., 1941). To survey the oxygen affinities of various invertebrate haemoglobins I therefore devised a method of working with one or two drops of whole, or very slightly diluted, blood. The method is as follows.
Dausend (1931) concluded from his experiments on the oxygen intake of Tubifex with normal and with carboxyhaemoglobin in waters of decreasing oxygen content that the haemoglobin in the blood remains fully oxy genated down to an oxygen pressure in the water of about 12 mm. at 19°C.
