According to the Houyhnhnms host, what are the limitations of Gulliver's anatomy in Gulliver's Travels?

In the
fourth book of , Gulliver lands on an island inhabited by rational horses,
who keep the humanlike Yahoo as animals, much as humans have kept domesticated animals such as
horses. To the Houyhnhnms, the horse represents the apex of nature (in fact, according to
Gulliver, the word signifies "in its etymology, the Perfection of
Nature" (Swift, Gulliver's Travels, Penguin Classics Ed.
(paperback), New York: Penguin Books, 1985, 281). This reflects the terms by which Gulliver
himself is viewed. To the Houyhnhnms, Gulliver is nothing more than a particularly intelligent
yahoo (in fact, he is referred to as "a perfect Yahoo" (283)).

An
earlier answer has already cited Gulliver's conversation in chapter 4, during which the
Houyhnhnm makes an account of Gulliver's anatomical limitations. He proceeds to cite the
uselessness of Gulliver's nails and criticizes Gulliver's bipedal nature; he...