Cynoglossums contain livertoxic pyrrolizidine alkaloids. Read more here. -Henriette
A tall and singular looking plant, frequent by our way sides, and distinguished by its large whitish leaves, and small purple flowers, as also by the particularity of its smell, which has been supposed to resemble that of a kennel of hounds. It is two feet and a half high. The stalk is angulated, firm, and upright: the leaves are long, considerably broad, and of a pale whitish or bluish green colour, sharp at the points, and not at all serrated at the edges. The flowers are small, and of a deep purple: they grow along the tops of the branches, and are followed by rough seeds.
The root is the part used; it is long, thick, and brown, but whitish within; it is balsamic and astringent. Given in decoction, it is excellent against coughs arising from a thin sharp humour. Dried and powdered, it is good against purging, and stops the overflowing of the menses.