科学实验表明：同是在实验器皿中培育的心脏细胞，如果为心脏细胞提供生长所需的营养，并将新陈代谢的废物和外界的毒素垃圾及时清理掉，心脏细胞的存活时间就很长；相反，如果不能为心脏细胞补充营养、清理废物，提供适宜的生长环境，那么细胞将很快死亡。《黄帝内经·灵枢》中讲到："智者之养生也，必顺四时而适寒暑，和喜怒而安居处，节阴阳而调刚柔。如是，则避邪不至，长生久视。"实际上，人体得病，最为关键的在于外邪的入侵：例如"风邪"与"湿邪"。如果我们能清除或避开这些邪风贼气，就可以"长生久视"，"长生"就是活得时间长，老也不死；"久视"就是耳不聋，眼不花，闻花赏蝶；"长生久视"也就是有质量的长寿。( It's shown in scientific experiments that if heart cells cultivated in the experimental vessel are provided with the needed nutrients in their growth and cleared away the metabolic waste and the external toxins and waste in time, their survival time will be very long; on the contrary, if they aren't supplied with nutrients, cleared away waste and provided with a suitable growth environment, they will die very soon. It's said in "Divine Pivot of the Emperor's Inner Canon," "A wise man who knows how to preserve his health must first adapt to the climatic changes of four seasons, adjust his moods to the climatic changes rather than be subject to the changing moods and try to be placid instead of being self-willed. In this way, pathogenic factors can be eliminated and he can enjoy a long life and have good ears and eyes." In fact, the invasion of the external pathogenic factors is the most critical reason of the human disease, such as "wind pathogen" and "dampness pathogen." If we can eliminate or avoid these pathogenic and evil factors, we can "enjoy a long life." "Enjoying a long life" means a person lives long; "having good ears and eyes" means that a person whose eyes aren't faded and ears aren't deaf can smell flowers and appreciate butterflies; if a person can "enjoy a long life and have good ears and eyes," meaning that he has high-quality longevity.)