1] MODIFICATION OF VITAL ACTIONS 13 



Gastropoda (Dolium, Cassis, Tritonium, Natica heros) secrete 

 2% to 3% H 2 SO 4 . (LoEW.) 



To organic acids many algse are little resistant. Thus Spiro- 

 gyra and Splueroplea die in 0.1% malic or tartaric acid after 

 30 minutes ; in 0.05% malic or tartaric acid after 24 hours ; in 

 0.01% of these same acids in a few days. Formic acid pre- 

 vents development of bacteria even in small percents 0.05% 

 to 0.006%. On the other hand, some protoplasm has acquired 

 a resistance to organic acids. The vinegar eel - - Rhabditis 

 aceti lives in 4% acetic acid. The protoplasm of the Dro- 

 sera tentacle resists 0.23% tartaric, citric, and other organic 

 acids. 



b. Soluble mineral bases, including those of corrosive alkalies 

 and the alkaline earths : Ca, Ba, and Sr. The corrosive alka- 

 lies cause a swelling of the protoplasm, but the primary effect 

 is rather a chemical one. (Cf. FROMANN, '84, p. 90.) 



The lower water animals and plants are quickly killed by 

 0.1% potassic or sodic hydrate. Thus, the movements of 

 Chara cease in 0.05% KOH in 35 minutes. Bacteria are more 

 resistant ; the limit for the typhus bacilli being between 0.10% 

 and 0.14%, and for the cholera bacillus, between 0.14% and 

 0.18%. Ascaris is still more resistant, living for 20 minutes 

 in a 2% solution of NaOH. 



CaO is still more powerful. A 0.007% to 0.025% solution 

 in bouillon kills bacilli. A 0.013% solution is fatal to algse 

 like Spirogyra. 



K 2 CO 3 kills bacteria in 0.8% to 1.0% solutions. 



Na 2 CO 3 kills Ascaris in a 5.8% solution after 5 to 6 hours. 

 (LoEW, '93, pp. 33, 34.) FROMANN has discussed the histo- 

 logical changes in protoplasm after treatment in Na 2 CO 3 . 



It is difficult to say whether the action of some of these re- 

 agents may not be an osmotic, rather than a chemical one. 

 The action of Na 2 CO 3 , for example, as described by FROM ANN, 

 is very similar to that of NaCl, whose action is probably solely 

 osmotic. 



c. Salts of Heavy Metals. The method of action of these 

 poisons has been accounted for upon the following grounds : 

 When amido-acids (which are found as disintegration products 

 of all animal tissues) are treated with salts of the heavy metals, 



