Observations upon the reducing substances of pigeons' blood

Abstract

that the total reducing value of normal avian blood is considerably higher than that of normal mammalian blood; in fact this value, when expressed in terms of glucose, seems to show that the sugar level in normal birds is roughly the same as that which is characteristic of human diabetics. Schwarz and Heinrich, for example, found that the average total reducing value of hens' blood was as high as 253 mg. of glucose per 100 cc. when estimated by the Hagedorn and Jensen method. Marrian et al. obtained values of 180 mg. per 100 cc. for pigeons deprived of food for 24 hours. Collazo found 210 mg. of glucose per 100 cc. for pigeons; and Riddle and Honeywell observed variations in the sugar level according to the breed of pigeons used, their values lying between 149 and 258 mg. of glucose per 100 cc. The question therefore arises whether these high values are caused by an additional amount of glucose as compared with that of mammalian blood, or whether the non-glucose reducing substances in avian blood are present in amounts sufficient to lower the true glucose value to one approaching mammalian limits. Intimately connected with this problem are the unpub- lished observations (a) by Kinnersley and Peters, that the reducing value of the blood of pigeons in insuilin convulsions is about 70 mg. of glucose per 100 cc. when estimated by the Hagedorn and Jensen method; and (b) by J. T. Irving, that the apparent glucose content of pigeons' blood is about 60 mg. when glycolysis has proceeded until the reducing value has become constant. We take this opportunity to express our indebtedness to Dr. Irving for allowing us to mention his observations. These results seem to show that the amount of non-glucose reducing substances in pigeons' blood is con- siderable, and it is therefore important to ascertain their nature, relative proportions and, if possible, their function. This information is needed in order to decide what is the best method of estimating the blood-"glucose," but in addition unusual interest centres round the question of function, since