Horse outward similarity is an unreliable measure of relatedness. Besides the horse, there are six other species of genus "Equus" in the Equidae family. These are the ass or donkey, "Equus asinus"; the mountain zebra, "Equus zebra"; plains zebra, "Equus quagga"; Grévy's zebra, "Equus grevyi"; the kiang, "Equus kiang"; and the onager, "Equus hemionus". Horses can crossbreed with other members of their genus. The most common hybrid is the mule, a cross between a "jack" (male donkey) and a mare. A related hybrid, a hinny, is a cross between a stallion and a jenny (female donkey). Other hybrids include the zorse,
The Adventures of a Donkey Monthly Review" of 1752-1825 said it was an 'agreeable little book' which creates and interest for the promotion of humanity. The 1806-1819 edition of "The Literary Panorama" thought it should be regarded favourably due to Argus' contribution to donkey welfare by introducing children to the mishaps which can occur from maltreatment, stating, '…[Argus'] imagination has exercised itself in favour of the rising generation.' And, 'it is an act of benevolence to call youthful attention to their [donkeys] necessities, and to contribute in a proper degree to their comforts by good usage.' Other publications, such as the 1833 edition of "The