> 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 hoof which came from the Old English hof.