Definition of "castoreum"

One of the substances tried was castoreum. […] If I were to judge from my own experience, I would say castoreum has very little therapeutic power, for I have not seen much benefit from its employment in those cases to which this remedy is said to be adapted.

1835 November 28, Jon Pereira, “Lectures on Materia Medica, or Pharmacology, and General Therapeutics: Lecture IX: On Castoreum”, in London Medical Gazette, volume 17, page 299

While the role of castoreum as a means of territorial advertisement has been extensively investigated and supported, the possibility of coding for sex information has not yet been excluded.

1999, L. Sun, D. Müller-Schwarze, “Chemical Signals in the Beaver: One Species, Two Secretions, Many Functions?”, in Robert E. Johnston, Dietland Müller-Schwarze, Peter W. Sorenson, editors, Advances in Chemical Signals in Vertebrates, page 284

Synthetic castoreums are now available, and can be as good as the natural fragrant[sic].

2004, Christian V. Stevens, Roland Verhé, Renewable Bioresources: Scope and Modification for Non-Food Applications, page 257