Further Investigation on the Transmission of Induced Tumors in Fowls

The possibility that the fowl tumor agents are of endogenous origin has been frequently suggested but no definite evidence for this idea has been produced. The demonstration of transmitting agents in induced tumors while not absolutely proof might be considered as giving support for such a conclusion. In i9u 5 Murphy and Landsteiner (9) reported the induction of two typical sarcomas in chickens by the injection of a high boiling point fraction of coal tar. One of these proved to be transplantable. It grew actively in new hosts, was highly invasive and metastasized freely. Repeated attempts to transmit this tumor by Berkefeld filtrates or desiccates gave negative results. In I928 Sturm and Murphy ( i4) reported further tests on transmission of this tumor in which modification of methods of filtration were used, and in which the products of filtration or desiccation were brought in contact with a variety of cell types, both in adult fowls and chick embryos. Again no evidence for an agent separable from the cell could be found. Peacock ( iu) failed to demonstrate transmissible agents in 7 strains of transplantable induced tumors or in 8 others which were not transplantable. Mellanby (6), and Rothbard and Herman ( i3) among others have reported similar results. In contrast to these negative findings McIntosb (4) in I933 reported that 3 out of his 4 transplantable induced chicken tumors were transmissible by filtrates. In I939 with Selbie (5) he added a second series in which 2 out of 4 induced chicken tumors could be transmitted by cell-free extracts. While there has been some criticism of McIntosh's experiments, there is no immediate explanation of this divergence from the results obtained by a group of other competent investigators. The methods of induction, the system used in transplantation and filtration did not vary essentially from those in general use. The point as to whether the induced fowl tumors do contain agents separable from the cell is so important, that we consider it essential for McIntosh's observations to be confirmed by others before it is accepted. The present report is an attempt in this direction.