Flourens, using his own formula, assigned the age of 150 years to elephants as their epiphyses do not fuse with the long bones until the age of 30. So far, I know of no fact to support the conclusion, although it seems fairly well established that occasionally an elephant may reach a century. It is stated that one elephant was in service throughout the whole period of more than 140 years in which Ceylon was occupied by the Dutch. This elephant was found in the stables in 1656. Natives with special knowledge of elephants set down their duration of life as from 80 to 150 years, but say that they begin to grow old at from 50 to 60 years of age. My general conclusion from the facts is that the life of these very large mammals is about the same as that of man who is very much smaller. Centenarians, extremely rare amongst elephants, do not appear to exist in any other kind of mammals except man. The rhinoceros, another large mammal which is a native of the same countries as the elephant, does not reach a great age. According to Oustalet an Indian rhinoceros died in the menagerie of the Paris Museum at about the age of 25 years, and showed all the signs of senility. Another Indian rhinoceros lived for 37 years in the London Zoological Gardens. Grindon has stated his opinion that the rhinoceros may live for 70 or 80 years, but this seems rather an inference from the slowness of growth than a statement of observed fact. Horses and cattle are large animals, but do not enjoy very long lives. The usual duration of life in horses is from 15 to 30 years. They begin to grow old about 10 years, and in very rare cases may reach 40 or more. A Welsh pony is said to have reached the age of sixty, but such a case is excessively rare. Two other extreme cases are that of a horse belonging to the Bishop of Metz which died at the age of 50 years, and the charger of Field-Marshal Lacy which died at 46. The duration of life of cattle is still shorter. Domestic cattle show the first sign of age, a yellow discoloration of the teeth, when five years old. In the sixteenth to eighteenth year the teeth fall out, or break, and the cow ceases to give milk, whilst the bull has lost reproductive power. According to Brehm, cattle live for 25 to 30 years or more. Although the duration of life is short, cattle are not prolific. The gestation period of a cow approaches that of the human race (242-287 days), and there is only one birth a year. The total period of reproductivity lasts only a few years. The sheep, another domesticated Ruminant, has a life even shorter. According to Grindon, sheep do not live longer than 12 years as a rule, but may reach 14 years, which in their case would be extreme age, as they generally lose their teeth at from 8 to 10 years. Some Ruminants, such as camels and deer, apparently live longer than sheep or cattle, but I do not know exact facts about them.