§1] MODIFICATION OF VITAL ACTIONS 5 



to act by oxidizing the protoplasm. Thus HjAsOj can take 

 up free oxygen as it would be found in water, and it can part 

 with it readily to the protoplasm, thus oxidizing and eventually 

 wholly consuming it. Such is one theory of its action. A few 

 words as to effects upon Protista: Infusoria survive in 0.1% 

 potassic arsenite in spring water only a short time, but live 

 for weeks in a 0.1% solution of the potassic arsenate. (LoEW, 

 '83, p. 112.) Algae (Spirogyra) are killed by a 0.1% solution 

 of potassic arsenite in six days, — the protoplasm contracts and 

 shows formation of granules, the death of the chlorophyll bands 

 preceding that of the cytoplasm. The same solution of potassic 

 arsenate, meantime, shows no injurious action, (LoEW, '87, 

 p. 445. ) Still other arsenious acid salts tried upon other algae 

 (Zygnema, Diatomacea), upon Infusoria, and upon tadpoles 

 showed themselves, uniformly, more powerful agents than the 

 corresponding arsenic salts. The lower fungi are only slightly 

 affected by arsenious salts ; not at all by those of arsenic acid. 



2. Hydrogen. — Kuhne ('64, p. 52) subjected Amoeba to H 

 for 24 minutes. At the end of that time, some individuals 

 had assumed a spherical shape, others appeared unchanged in 

 form, but were motionless. Similar results were obtained with 

 Actinophrys, the plasmodium stage of Myxomycetes, and with 

 the stamen hairs of Tradescantia. 



Demoob ('94, p. 190) also experimented upon the latter 

 object, and his results are worth giving in detail.* During 

 the first moments of the passage of the gas, the protoplasmic 

 movements are slightly accelerated. Soon the protoplasm be- 

 comes very granular, and, after a variable time, 15 to 40 minutes, 

 is quiet. The aspect of the protoplasm at this time varies 

 with the character of the cell. If it is young, having a large 

 nucleus and without a primordial utricle, the protoplasm ap- 

 pears uniformly granular. If, on the contrary, the cell possesses 

 a great reserve of water, with long, protoplasmic filaments, 

 the protoplasmic granules become more refringent, increase in 

 volume, and accumulate around the nucleus, — the peripheral 



* Method : The hydrogen gas may be generated in a Kipp's apparatus, and 

 should pass through a series of washing flasks containing, e.g., solutions of potash 

 and acetate of lead. See Verworn : AUgemeine Physiol., p. 285. Demoor 

 kept his stamen hairs in sugared water in an Engelmann's chamber. 



