Hartshorn n. : The horn or antler of the hart, or male red deer.

Hartshorn n. : Spirits of hartshorn (see below); volatile salts.

Example:
Have you read Charles Hartshorn's book, "Wisdom as the middle way" or whatever it's called? It's not bad.?

Taxonomy
hartshorn, ammonia, salt of hartshorn, ammonium carbonate, Phelps Brown, spirit of hartshorn, hooves and horns, acrylamide, free encyclopedia, baking powder, male red deer, baker's ammonia, animal oil, ammonium chloride, aqueous solution, detergent, used to treat, treatment.

Defination from the web:
hartshorn is a crude animal oil obtained from the destructive distillation of the deers' bones or horns. The salt of hartshorn actually refers to two distinct substances, sal ammoniac (ammonium chloride), and ... teaspoon of hartshorn equals to 1 teaspoon of baking powder. ...