I believe the appropriate answer is a cooling-off period. The cooling off period us described as the state of returning to the offender's usual way of life between homicides. The key distinction between the serial killers and mass or spree killers is this emotional cooling off period in which the killer blends back into his/her normal life.
Once food is in the small intestine, it stimulates the pancreas to release fluid containing a high concentration of bicarbonate. This fluid neutralizes the highly acidic gastric juice, which would otherwise damage the membrane lining of the intestine, resulting in a duodenal ulcer.
Hope it Helped.
The principle is called CEPHALOCAUDAL PRINCIPLE.
This principle proposed that growth follow a particular pattern in which the head and the upper part of the body grow first before the growth proceeds to other part of the body.
