This is a quote from the book "The Virtue Of Selfishness" by Ayn Rand
...an be seen in the rare, freak cases of children who are born without the capacity to experience physical pain; such children do not survive for long; they have no means of discovering what can i
njure them, no warning signals, and thus a minor cut can develop into a deadly infection, or a major illness can remain undetected until it is too late to fight it.
read full book
�� for those living organisms which possess it — is the basic means of survival.
The simpler organisms, such as plants, can survive by means of their automatic physical functions...