Complex sectioning (transverse) at mid pons level along with vagi results in

→ Section A: Cut at upper part of pons: (Decerebration): Normal rhythmic breathing continues. Loss of voluntary breath holding. If vagi are cut, increase in depth and slow breathing. → Section B: Cut at mid-pons: Apneustic center (Ap) intact but pneumotaxic centre separated. Ap stimulates Inspiratory (I) neurons, which increase depth of breathing. Vagi intact: Regular respiration with deep and slow breathing (increase in TV and a slight decrease in RR). Vagi cut: Arrest of respiration in maximum inspiratory phase (apneusis) interrupted by brief expiration. → Section C: Cut at inferior portion of pons: All the pontine tissue is separated Vagi intact: Irregular and gasping but it is rhythmic (because pacemaker tissue is intact). Vagi cut: Same effect as above, because vagi are connected to Ap center. → Section D: Cut below medulla: Complete transection of brainstem: Stops all respiration (apnoea and death). Bilateral vagotomy only: Regular respiration with deep and slow breathing (increase in TV and a slight decrease in RR).