- Ungulate is a term for any hoofed mammal.
- The word unguis is a noun that refers to a nail, claw,
hoof, or clawlike structure.
- Cows are considered even-toed ungulates. (Pigs, camels, and deer
are also even-toed ungulates.)
- The hoof consists of hornlike dermal (skin) tissue, comparable to the human fingernail.
- This hornlike tissue (unguis) extends over the end of a broadened terminal digit.
- The hoof is made up of keratin (which also makes up hair, nails, horn, wool, and feathers).
- Keratin is a fibrous protein.
- Of the amino acids in keratin, cystine may account for up to 24%.
- The numerous disulfide bonds formed by cystine cause keratin
to be very stable.
- Keratin is not water soluable, and it is not able to be attacked by the
various enzymes that break up proteins.
- The modern English word hoof is decended from the Middle
English word (also hoof) which came from the Old English
Source: http://www.brittanica.com, entries Ungulate, Hoof, Keratin.