一、引言一切生物生活在自然界中,寿命长短不一,但每一种动物的寿命总有一个最高限度,如小鼠约为三年,狗约为20年,马约为40年,人约为110年。虽然人有能活到150岁的报道,但毕竟是稀少的。在群体中平均寿命总是比最高限度小的多,每种动物间的个体差异很大,每种动物的不同品系,寿命长短也相差悬殊。如以小鼠而论,新西兰黑鼠的纯 I. INTRODUCTION All living creatures live in nature with different life expectancy. However, the life span of each animal has a maximum limit of about three years for mice, about 20 years for dogs and about 40 years for horses. For 110 years. Although people can live to 150-year-old report, but after all, is scarce. The average life expectancy in a population is always less than the maximum limit, and the individual differences between each animal are very large. The different strains of each animal also differ in their length of life. As in mice, New Zealand black rats pure