The 21 nocturnes are more structured, and of greater emotional depth, than those of Field (whom Chopin met in 1833). Many of the Chopin nocturnes have middle sections marked by agitated expression (and often making very difficult demands on the performer) which heightens their dramatic character.
What is it about the middle of Chopin's nocturnes that increases their drama?
agitated expression

The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. Only a few invertebrates such as sponges, jellyfish, adult sea squirts and starfish do not have a brain; diffuse or localised nerve nets are present instead. The brain is located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste, and smell. The brain is the most complex organ in a vertebrate's body. In a typical human, the cerebral cortex (the largest part) is estimated to contain 15–33 billion neurons, each connected by synapses to several thousand other neurons. These neurons communicate with one another by means of long protoplasmic fibers called axons, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells.
In people, how many neurons make up the cerebral cortex?
15–33 billion

It was against this background of public anger that Jean Metzinger and Albert Gleizes wrote Du "Cubisme" (published by Eugène Figuière in 1912, translated to English and Russian in 1913). Among the works exhibited were Le Fauconnier's vast composition Les Montagnards attaqués par des ours (Mountaineers Attacked by Bears) now at Rhode Island School of Design Museum, Joseph Csaky's Deux Femme, Two Women (a sculpture now lost), in addition to the highly abstract paintings by Kupka, Amorpha (The National Gallery, Prague), and Picabia, La Source, The Spring (Museum of Modern Art, New York).
In what year was  Du "Cubisme" published?
1912