POISONOUS PROTEINACEOUS SUBSTANCES 55 



84. Toxic Effect of Phenol. Make up a .5 per-cent. solution 

 of carbolic acid (phenol) in distilled water, and drop into it fresh 

 strips of leaves of Oxalis, noting length of time necessary to pro- 

 duce death as indicated by discoloration of the leaf. Place some 

 filaments of Spirogyra in a solution of equal strength and note 

 results in three hours and a day later. Note changes in cell 

 structures. Make a series of decreasing intensity and determine 

 in what concentration the alga may survive. The low conduc- 

 tivity of phenol shows that practically no dissociation occurs. 

 Phenol is a poison to the higher animals by inducing paralysis of 

 the nerve centers, and also works direct injury to the cells with 

 which it comes in contact. 1 



85. Toxic Action of Phloroglucin. Repeat 84 with solutions 

 of phloroglucin and fix the limit of toxic acid of this substance. 

 Compare its action with that of phenol. 



86. Toxic Action of Formaldehyde. Place a small lot of 

 Spirogyra in a culture dish containing water from a stream, 

 and sufficient formaldehyde to make a .01 per-cent. solution. 

 Examine from day to day and note length of time the alga 

 may endure this concentration. Make similar tests with solu- 

 tions more and less dilute. Test also with seedlings of lupine as 

 in 75. 



87. Poisonous Proteinaceous Substances. A large number of 

 proteinaceous compounds secreted by plants are well known as 

 deadly poisons to the higher animals. Many of them are un- 

 stable and act as substitution poisons upon protoplasm. Their 

 action upon the higher organisms among animals consists of 

 special disturbances of the nerve centers in many instances. Such 

 compounds do not pass the cellulose and protoplastic membranes 

 of the plant with great readiness, but in experimental tests in plant 

 cultures disintegration often ensues with the result that simpler, 

 more easily dialyzable, substances are formed that exert a direct, 

 or indirect toxic action. 



1 True and Kunkel. The poisonous effect exerted on living plants by phenols. 

 Bot. Centralbl. 76: 289, 321, 361. 1898. . 



