. Handbook of medical entomology. Insect pests; Insects as carriers of disease; Medical parasitology. 2 24 Arthropods as Essential Hosts of Pathogenic Protozoa this field contracted tlie disease. The fourth animal was not examined as to its blood but it showed no external symptoms of the disease. In these earher 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 ob- tained the parasite from the blood of its host and in its dissolution on the pasture a certain r
. Handbook of medical entomology. Insect pests; Insects as carriers of disease; Medical parasitology. 2 24 Arthropods as Essential Hosts of Pathogenic Protozoa this field contracted tlie disease. The fourth animal was not examined as to its blood but it showed no external symptoms of the disease. In these earher 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 ob- tained 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 ; The feeding of one animal for some time with grass from the most abundantly. /} â shield Chitmiz&ci points 140. Hyalomma aegypticum. After Nuttall and Warburton. 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 dis- integrating 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 mani- fested itself. It was conveyed by the progeny of ticks which had dropped from the Southern cattle and deposited their eggs on the Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Riley, William A. (William Albert), b. 1876; Johanssen, Oskar Augustus, 1870-. Ithaca, N. Y.
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