Watch Me Pull A Rabbit out of my Biretta!

 From McNamara's Blog:

The Rail Splitter was one of several anti-Catholic publications that gained a wide circulation in the 1910′s and 1920′s. This cartoon from its pages shows a cassocked priest replete with horns and tail knocking at the door of the American public school system. (In many remote rural areas of the South, priests, and Catholics in general, were said to have horns under their hats). He is seen literally crossing the line between Church and State, coming from the “parochial school and nunnery,” where “superstition,” “ignorance,” and “despotism” are said to dwell abundantly. A common theme in the anti-Catholicism of this era was the alleged Catholic attempt to subvert the American public school system and replace it with parochial schools subservient to Rome rather than the State. References are made to the Spanish Inquisition and its alleged torture devices, such as the thumb screw. 

When he writes "horns under their hats", I assume he means under their birettas".