Breschet made many contributions in comparative anatomy and in his research of zoonotic diseases.
Also, he was the first to create an accurate figure of the rete mirabile in whales and dolphins, a vascular network that allows these mammals to survive and adapt in ocean depths; a feature discovered by Edward Tyson.
He did extensive anatomical studies of veins of the cranium and spine, and made important investigations of the auditory system in vertebrates.
He provided a comprehensive description of the utricle and saccule of the inner ear, and is credited for introducing the terms "otoconia" and "helicotrema".
Breschet has several other anatomical terms named after him, including: In 1842, he was elected a foreign member of the Royal Swedish Academy of Sciences.