Respiration, Digestion, and Fermentation. in 



secretion of Cypripedium has been found to be irritable to 

 the skin, the volatile secretions of poison ivy have a marked 

 poisonous effect, and the unpleasant effects from the stinging 

 hairs of nettle are well known. In the latter instance the 

 secretion is contained in the stiff hairs borne on the leaves 

 and stems ; and when the walls are broken, the jagged edges 

 penetrate the skin, allowing the action of the irritating con- 

 tents to act more strongly. Secure fresh stems and leaves of 

 Primula, Cypripedium, or nettle, and make tests to ascertain 

 the presence of oils or acids in the glandular hairs. 



