On the Experimental Production of Edema in Larval and Adult Anura

Edematous frog larvm are among the commonest types of abnormalities which can be produced by experimental means. When ova of the twoor four-celled stage are placed in solutions of potassium cyanide, acetone, butyric acid, or ethyl alcohol for from 12 to 24 hours, and then subsequently developed in t ap water, an edema, tous condition of the body frequently, though not always, results. Hertwig 1 has produced such larvae by exposing early cleavage stages to the influence of radium. An edematous condition of the body also occasionally results when ova are allowed to develop in direct sunlight in the laboratory and may even be met with among the controls. The life of such larvm is relatively short. The edematous frog larvm thus far observed by the writer can be grouped into two main types: Type 1, in which, with the exception of their general edematous condition, the frog larvm appear externally to be otherwise normally developed; Type 2, in which some marked abnormality, especially of the head region and vascular system, usually accompanies an edematous condition of the body. All the larvm referred to in this paper were in the stage at which the pronephros acts as the functional kidney and in which the mesonephros is either not at all developed, or is represented only by its earliest anlage. An examination of serial sections of a large number of both types of edematous frog larvm shows that in all cases, and without exception, there is a marked deficiency evident in the development of certain specified tubules in the pronephros. Reconstructions after the method of Born clearly indicate that this deficiency is associated with the