Institutio Oratoria

But when three fingers are doubled under the thumb, the finger, which Cicero [*](de Or. II. xlv. 188. ) says that Crassus used to such effect, is extended. It is used in denunciation and in indication (whence its name of index finger), while if it be slightly dropped after the hand has been raised toward the shoulder, it signifies affirmation, and if pointed as it were face downwards toward the ground, it expresses insistence. It is sometimes also used to indicate number.

Again, if its top joint is lightly gripped on either side, with the two outer fingers slightly curved, the little finger rather less than the third, we shall have a gesture well suited for argument. But for this purpose the same gesture is rendered more emphatic by holding the middle joint of the finger and contracting the last two fingers still further to match the lower position of the middle finger and thumb.