Saliva

It is interesting to me the difference between spit and saliva.  Saliva is in your mouth and is valuable to life.  But as soon as it leaves your mouth it becomes spit and is thought of as vile and nasty.  In reality the only difference is that spit is out of your mouth.  Society has shaped us into thinking that spitting is nasty and wrong.  This is an example on how society has shaped our mind