A vegetarian is a person who eats no flesh. There are subcategories, such as lacto-vegetarians and ova-vegetarians, who eat no flesh but who eat some of the products of animals – in these cases, milk and eggs respectively. A vegan, on the other hand, not only refuses flesh, but also abstains from eating and sometimes wearing all animal products. Vegans argue that animal products cannot be separated from animal mistreatment. They point, for instance, to the connections between eating eggs and the keeping of hens in battery cages, and between drinking milk and the breeding and slaughter of veal calves, which are necessary to keep dairy cows in milk. For the same reason, many vegans also refuse to wear or use products based on animal material such as soap, wool and leather. They make the point that it would be considered by a vegetarian unsuitable to be entertained on a leather seat. Other variations are vegetarians who will eat free-range eggs but refuse milk, and others who will eat fish but refuse the flesh of other animals. In spite of problems of definition, there have been several attempts to calculate the extent of vegetarianism in a number of countries, but the data available for countries such as the United Kingdom and the United States are few.