老年疾病通长都不是起于外因的。
野生动物濒危的原因可分为外因和内因，外因多是人为因素造成，而内因主要是遗传衰竭、疾病等。
The reason of endangered wild animals can be divided into the external and internal. External is caused by man-made factors, internal is genetic failure and disease.
疾病的发生，其根本是在内、外因素作用下，人的整体功能失去动态平衡。
The fundamental reason for illness is that various internal and external factors disturb the dynamic balance.
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