The uptake and distribution of radioactive phosphorus in chicken eggs containing a rapidly growing mammary tumor of a C3H mouse.

Tumors of rats and especially of mice have been grown in chicken eggs for a number of years. Tu mors of sufficient size and uniformity as to be used in chemotherapy have been produced by the yolk sac technic, whereby the maccrated tumor is in jected into the yolk sac. The advantages of such a technic for screening chemicals for any tumor inhibiting effects have already been pointed out by Taylor (1) and thus will he reviewed here only briefly. The rapidly growing tumor and chick embryo grow within the closed system of the egg, sharing the same blood stream but without any physical contact between the two. It is thus possible to in ject a substance between the egg shell and the chorio-allantoic membrane (analogous to a subcu taneous injection in mice) and, by weighing the tumor and chick embryo of both control and treated eggs, to determine whether the substance (a) has no effect, (b) inhibits tumor growth spe cifically, (c) inhibits embryo growth specifically, or (d) inhibits fast-growing tissues, in general. The following experiments were undertaken to determine the manner of uptake and distribution of a substance injected between the chorio-allan toic membrane and the egg shell. For this purpose radioactive phosphorus in the form of Na2HPO4 was used.