Of fourteen head of native cattle placed in a field with tick-infested Northern cattle all but two contracted the disease. This experiment was repeated with similar results. Four head of native cattle kept in a plot with three North Carolina cattle which had been carefully freed from ticks remained healthy. A second experiment the same year gave similar results. Still more conclusive was the experiment showing that fields which had not been entered by Southern cattle but which had been infected by mature ticks taken from such animals would produce Texas fever in native cattle. On September 13, 1889, several thousand ticks collected from cattle in North Carolina three and four days before, were scattered in a small field near Washington. Three out of four native animals placed in this field contracted the disease. The fourth animal was not examined as to its blood but it showed no external symptoms of the disease. [Illustration: 140. Hyalomma ægypticum. After Nuttall and Warburton.] In these earlier experiments it was believed that the cattle tick acted as a carrier of the disease between the Southern cattle and the _soil_ of the Northern pastures. "It was believed that the tick obtained the parasite from the blood of its host and in its dissolution on the pasture a certain resistant spore form was set free which produced the disease when taken in with the food." The feeding of one animal for some time with grass from the most abundantly infected field, without any appearance of the disease, made this hypothesis untenable. In the experimental work in 1890 the astonishing fact was brought out that the disease was conveyed neither by infected ticks disintegrating nor by their directly transferring the parasite, but that it was conveyed by the young hatched from eggs of infected ticks. In other words, the disease was hereditarily transferred to ticks of the second generation and they alone were capable of conveying it. Thus was explained the fact that Texas fever did not appear immediately along the route of Southern cattle being driven to Northern markets but that after a certain definite period it manifested itself. It was conveyed by the progeny of ticks which had dropped from the Southern cattle and deposited their eggs on the ground. These results have been fully confirmed by workers in different parts of the world,--notably by Koch, in Africa, and by Pound, in Australia. The disease is apparently transmitted by _Boophilus annulatus_ alone, in the United States, but it, or an almost identical disease, is conveyed by _Ixodes hexagonus_ in Norway, _Ixodes ricinus_ in Finland and France and by the three species, _Boophilus decoloratus_, _Hyalomma ægypticum_ (fig. 140 and 141), and _Hæmaphysalis punctata_ in Africa. [Illustration: 141. Hyalomma ægypticum. Capitulum of female; (_a_) dorsal, (_b_) ventral aspect.]