1: Pat oneself on the back verbally
9: Like Zero in 'Beetle Bailey'
18: English class concern
25: 'Run to ___' (Bobby Vee hit)
27: Stress symptom, perhaps
36: The Sail (southern constellation)
38: Silver Ghost, for short
42: Spanish title of respect
43: Grassy plains of Argentina
44: Green headgear in a 1968 movie
51: McIntosh or Granny Smith