Abstract
It has been found possible to produce hypoglycemia and hyperglycemia in the chick embryo. These experiments were carried out of 14 to 16 day embryos of the single combed white Leghorn variety. Immediately after the normal blood samples were taken, the injection was made into the air-sac from which absorption takes place into the blood stream of the respiratory capillary vascular network of the chorio-allantois.
The normal blood sugar of the chick embryo at this stage of incubation varies between 209 and 296 mg. per 100 cc. It appears that the glucose reaches its normally high level in birds at an early stage of development. The graph shows the effect of insulin upon the blood sugar. Riddle 1 has shown that adult birds survive thirty times the proportional amount of insulin required to kill a one kilogram rabbit. It is interesting to note that this resistance probably is established very early in the embryo. An important factor in this resistance is suggested by the hyperglycemia which is known to follow hemorrhage in the adult mammalian. That this occurs also in the chick embryo is shown by the dotted curve in the graph, obtained from an experiment in which no insulin was given. In an adult animal with a large volume of blood, the increase of sugar following blood sampling would be negligible, but in the case of the embryo with its comparatively small volume of blood, the taking of one-tenth cc. samples is a severe strain upon the embryonic physiological processes. The result is a marked hyperglycemia as shown, which would neutralize to some extent the hypoglycemic effects of insulin.
Very marked hyperglycemia may be produced by injecting a glucose solution into the air-sac as shown in Table 1.
Get full access to this article
View all access options for this article.