Tyrian purple by ancient authors. Not much is known about the subsequent steps, and the actual ancient method for mass-producing the two murex dyes has not yet been successfully reconstructed; this special "blackish clotted blood" colour, which was prized above all others, is believed to be achieved by double-dipping the cloth, once in the indigo dye of "H. trunculus" and once in the purple-red dye of "B. brandaris". The Roman mythographer Julius Pollux, writing in the 2nd century AD, asserted ("Onomasticon" I, 45–49) that the purple dye was first discovered by the philosopher Heracles of Tyre, or rather, by his dog, whose
Sabin–Feldman dye test (negative result). The dilution of the test serum at which 50% of the tachyzoites are thin, distorted and colorless is reported as antibody titer of the test serum. The test is highly sensitive and specific with no false positives reported so far. Drawbacks of this test: 1. Difficulty in maintaining the live tachyzoites. 2. It detects immunoglobulin G(IgG) antibodies, hence cannot differentiate between recent or past infection. Sabin–Feldman dye test A Sabin–Feldman dye test is a serologic test to diagnose for toxoplasmosis. The test is based on the presence of certain antibodies that prevent methylene blue dye from entering the