Properties of the Causative Agent of a Chicken Tumor Iii. Attempts at Isolation of the Active Principle* By
نویسنده
چکیده
Since the demonstration of the transmissibility of chicken tumors by agents separable from the malignant cells, the relationship of this group of neoplasms to those of the mammalian type has been a question of first importance. At first it was generally considered that the chicken tumor agents belonged to the virus group of organisms. This conclusion led to some doubt that the chicken tumors represented the same sort of disease as mammalian neoplasms, for there was no evidence that the latter were infectious processes. This difference, illustrated principally by the failure to transmit mammalian tumors by other means than actual grafts of living tumor cells, I deserves consideration on the basis of the fact that virus diseases are as a rule easily transmitted experimentally to susceptible animals. Yet even mice, which are particularly receptive to inoculated tumors, show no response to injection of tumor extracts free from living tumor cells. The factual basis on which the chicken tumor agents are classified as viruses requires close examination in our opinion, for there are some properties of this group difficult to reconcile with such an assumption. The variety of types of chicken tumors, each transmitted faithfully
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