Rutherford did not discover any subatomic particles in 1919. He is famous for his discovery of the atomic nucleus in 1911, not for discovering new particles.

However, in 1919, Rutherford did conduct experiments that led to the transmutation of nitrogen into oxygen, a groundbreaking discovery in nuclear physics. This was the first time a naturally occurring element was artificially transformed into another, and it was achieved by bombarding nitrogen atoms with alpha particles. This experiment was crucial in understanding the structure of the atom and the nature of radioactive decay.

While he didn't discover a new subatomic particle in 1919, his work was instrumental in our understanding of the nucleus and its components.