皮肤很敏感,不仅表面有数不清的汗毛,就连微风吹动它都能感觉到,而且表皮下有非常丰富的神经纤维和各种各样的感觉细胞,能感受触觉、痛觉和温觉。但是,神经纤维并不直接暴露在外,而是躲藏在皮肤里面。通常打一拳,捏一把,被打、被捏的那一部分皮肤会觉得痛。不过,痛的时间很短,因为它受到皮肤的保护,不容易长时间地受到刺激。要是皮肤破了,有了伤口,那就不同了。敏感的痛觉神经纤维在伤口处暴露出来,各种各样的刺激都会影响到它,引起疼痛。咸的东西里面含有盐分,盐分浓度较 The skin is very sensitive, not only the surface has countless hairs, even the breeze blowing it can feel it, and the epidermis is very rich in nerve fibers and a variety of sensory cells, can feel the touch, pain and temperature sense. However, the nerve fiber is not directly exposed, but hide in the skin inside. Usually punch, pinch, beaten, pinched part of the skin will feel pain. However, the pain is very short, because it is protected by the skin and not easily irritated for a long time. If the skin is broken, with a wound, it is different. Sensitive pain nerve fibers exposed in the wound, a variety of stimuli will affect it, causing pain. Salty things which contain salt, salt concentration