Sentence:  [I]f the czigithai is not the ſame with the zebra, it may be the Aſiatic animal called <WSD>"onager</WSD>" or "wild aſs". The <WSD>onager</WSD> ſhould not be confounded with the zebra; but I am uncertain whether the ſame remark is applicable to the <WSD>onager</WSD> and czigithai; for, from comparing the relations of travellers, it appears, that there are different kinds of wild aſſes, of which the <WSD>onager</WSD> is the moſt remarkable. [...] The ſwiftneſs of the <WSD>onager</WSD> is mentioned by travellers, who remark, that he runs with ſuch rapidity as to eſcape the hunters, though mounted on horſes; [...] 
Meaning of the word marked with <WSD> tags:  The Asiatic wild ass or hemione ("Equus hemionus"), an animal of the horse family native to Asia; specifically, the (Persian onager), (Persian wild ass), or (Persian zebra) ("(Equus hemionus onager)").