Annual report of the Board of Regents of the Smithsonian Institution . espirochsetosis, due to S. theileri^ whichFig. 11.—Two spirochats of a was observed in the Transvaal by Theilerbat. The rounded figures rep- ^^^ -^^ ^j^g Cameroous by Ziemanu, is resent blood corpuscles. En- • i i . , 7 largement: 2,000. After Nic- Carried by Rhiiyicepfialus decoloratus oiie and comte. (Theiler, Confirmed by Laveran and Vallee, 1905). It is probably the same for S. ovina, which has been found in the blood of sheep in Erythrea and in the Transvaal (Theiler). C. Beartivater.—Finally,to close this list, which
Annual report of the Board of Regents of the Smithsonian Institution . espirochsetosis, due to S. theileri^ whichFig. 11.—Two spirochats of a was observed in the Transvaal by Theilerbat. The rounded figures rep- ^^^ -^^ ^j^g Cameroous by Ziemanu, is resent blood corpuscles. En- • i i . , 7 largement: 2,000. After Nic- Carried by Rhiiyicepfialus decoloratus oiie and comte. (Theiler, Confirmed by Laveran and Vallee, 1905). It is probably the same for S. ovina, which has been found in the blood of sheep in Erythrea and in the Transvaal (Theiler). C. Beartivater.—Finally,to close this list, which isalready too long, it isnecessary to add a disease,the origin of which is quitedifl^erent from that of thepreceding ones. This af-fection, which afflicts SouthAfrican ruminants, is due,like yellow fever, to an in-visible microbe, and Louns-bury, the expert entomolo-gist of the Cape govern-ment, showed in 1905 thatit is propagated by a tickallied to the ixodids, A/u-hlyomma hebreum. Suchin its entirety is the patho-genic work of the this Fin. 12.—Dermacentor reticulatus. Male. Veulralaspect. After Salmon and Sliles. Let us now see the minute mechanism THE MECHANISM OF THE PATHOGENIC ACTION. The role of the ticks in the transmission of piroplasmosis andspirochaitosis is to-day irrefutably demonstrated as much by fact asby observation and experience. Notwithstanding, it is contested by RELATION OF ARTHROPODS TO PATHOLOGY MAROTEL. 717 some biologists, at whose head is an indefatigable practitioner, Meg-nin, who, to the time of his death, remained one of the most ardentand persevering adversaries of the ixodid theory. It is necessary toconfess that this hesitation is comprehensible, becanse a goodly partof the history of the intimate mechanism of this transmission stillescapes us, while another part is very strange. However, here are some of the peculiarities which are observed: (a) The study of the evolution of ticks has shown us that in specieshaving
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