In order
to treat and research pain, health workers and scientists need to be able to use
some kind of measure other than relying on vocal indicators such as crying and
observation.  Another indicator has been
to use language as descriptors of pain, for example in the research of Melzaka and
Wall (1988).  These signs, whilst
extremely useful cannot be relied on alone, therefore we must examine the biological
process of the pain pathway.  When there
is an injury, for example a cut to the finger, 
sensory neurons which respond to the injury carry this information along
the peripheral nerve to the spinal cord. 
Chemical messages called neurotransmitters pass from the spinal cord to
the thalamus, this part of the brain then relays signals to the somatosensory
cortex, the part of the brain that is responsible for any physical sensation –
this process is called the spinothalamic pathway.