• 
  Montagu Love

  Dr. Blake
• 
  Richard Ainley

  Dr. Hale
• 
  Billy Bevan

  Chivers
• 
  Donald Crisp

  Dr. Drewett
• 
  Geraldine Fitzgerald

  Dr. Mary Murray
• 
  G.P. Huntley

  Dr. Thornton (as George P. Huntley Jr.)
• 
  Bruce Lester

  Dr. Bentley
• 
  Doris Lloyd

  Mrs. Foster

• 
  Leonard Mudie

  Mr. Foster
• 
  Barbara O'Neil

  Miss Leeming
• 
  Frank Reicher

  Dr. Esterhazy
• 
  Sig Ruman

  Professor Herman Von Reiter
• 
  James Stephenson (I)

  Dr. Paul Venner
• 
  Hermine Sterler

  Miss Hoffman
• 
  Clare Verdera

  Miss Dennis