No. 19.
This étude begins lightly spiccato at the middle of the bow. With the crescendo the necessity for a broader stroke arises, and we dispense with the spiccato. The following passage is played toward the middle of the bow the stroke becoming a spiccato:
Keep in the upper third of the bow when the tied notes are alternately long and short. In the seventh line, second measure, play the staccato run at the point of the bow: