Sera puppies weaned from, specific pathogen-derived hysterectomy free (SPF) closed dog colony does not contain antibodies against TGE virus related or serologically related, but the sera of puppies and dogs that are older than the open cage did. A ntivirus higher titer in the Rat Serum Albumin serum of older dogs suggest that these animals have suffered from either persistent or recurrent infection. Seventy-two puppies have had no contact with pigs, suggesting that the virus can spread independently of any contact with pigs. Tumor-blocking and -inhibitory serum factor in the clinical course canine venereal tumor. An in vitro method for growing colonies of cells in a tumor dog sex transplantabel semisolid agar described. Using autologous or homologous sera collected a normal dog as a feeder layer, 49.3 +/- 3.5 and 47.5 +/- 4.5 colonies of tumor is obtained, respectively, when 2 X 10 cells (4) tumors plated. With this test system, the assessment of the number of colonies provide fa...