有些是长期的动物的原因，生活和其他人短命，和，总之，在长度和生活简洁的原因展开调查。必要的开始我们的调查是关于这些问题的困难声明。因为它不在于动物和植物明确普遍它是一个单一的或多种原因，使得一些是长期居住，有些短暂。植物也有在某些情况下，寿命长，而在其他国家，但它持续了一年。此外，在一个长寿的天然结构和健全宪法一致，或者是独立的生命短促的不健康？也许在某些弊端案中，身体和生命的短暂疾病状态是可以互换的，而在其他病患者的健康是完全兼容的长寿命。睡眠和清醒，我们已经处理;生死，我们稍后会谈，同样对健康和疾病，只要它属于自然科学这样做。但目前我们调查的一些长途生物的原因，生活，和其他人短命的。我们认为这种区别不仅影响整个属，以整体，互相反对，但也适用于同种个体对照组。作为适用于属我请人与马的区别实例（人类具有比马的寿命），而在物种存在着人与人之间的差异，而男性也有一些是长期居住，其他人短命的，彼此在不同，他们住在不同区域的尊重。赛事栖息温暖的国家有较长的寿命，那些在寒冷的气候生活过短的时间。同样占领之间存在同一地区类似的个体差异。
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    THE reasons for some animals being long-lived and others short-lived, and, in a word, causes of the length and brevity of life call for investigation. The necessary beginning to our inquiry is a statement of the difficulties about these points. For it is not clear whether in animals and plants universally it is a single or diverse cause that makes some to be long-lived, others short-lived. Plants too have in some cases a long life, while in others it lasts but for a year. Further, in a natural structure are longevity and a sound constitution coincident, or is shortness of life independent of unhealthiness? Perhaps in the case of certain maladies a diseased state of the body and shortness of life are interchangeable, while in the case of others ill-health is perfectly compatible with long life. Of sleep and waking we have already treated; about life and death we shall speak later on, and likewise about health and disease, in so far as it belongs to the science of nature to do so. But at present we have to investigate the causes of some creatures being long-lived, and others short-lived. We find this distinction affecting not only entire genera opposed as wholes to one another, but applying also to contrasted sets of individuals within the same species. As an instance of the difference applying to the genus I give man and horse (for mankind has a longer life than the horse), while within the species there is the difference between man and man; for of men also some are long-lived, others short-lived, differing from each other in respect of the different regions in which they dwell. Races inhabiting warm countries have longer life, those living in a cold climate live a shorter time. Likewise there are similar differences among individuals occupying the same locality.