Complex sentence: In 1930, shortly after completing his internship, he began working in public health and was commissioned in 1934 in the United States Public Health Service and specialized in the epidemiology of sexually transmitted diseases.
Split into simpler sentences: In 1930, shortly after completing his internship, he began working in public health and was commissioned in 1934 in the United States Public Health Service. He specialized in the epidemiology of sexually transmitted diseases.