Abstract In a patent of 1920 by Hopkinson, there appears the claim that cotton thread need only be immersed in latex to bring about complete impregnation and even penetration of the latex into the canals of the fibers. This is a quite unwarranted claim, and it can be explained by the fact that Hopkinson was primarily a lawyer as far as patents are concerned, and there is a natural tendency in this profession to place a mortgage on future accomplishments. As a matter of fact, in spite of its very low viscosity (200 times less than that of benzene solutions containing the same percentage of rubber), latex does not penetrate spontaneously into textiles in the same way that clear solutions of rubber do. The work of Hauser and Hünemörder (cf. Rubber Chem. and Tech., 5, 685(1932)) has more or less settled this question. According to their technic, rubberized threads to be examined are immersed in gelatin, the preparation is frozen by carbon dioxide, and fine sections are cut by means of a microtome. The gelatin and also the cotton structure which has not been impregnated are then destroyed by concentrated sulfuric acid, and are eliminated by washing. The remaining rubber has a red-brown color. In this way Hauser and Hünemörder established definitely that whereas clear solutions containing, for example, five per cent of rubber, penetrate cotton threads, latex only coats them superficially and does not penetrate them.