28 CHEMICAL AGENTS AND PROTOPLASM [Cn. I 



tact with it ; while, by other persons, it may be taken into the 

 mouth with impunity. 



The phenomenon shown by man is found in other animals 

 also. Thus, among Invertebrates, although few bacteria can 

 resist 1% .Na 2 CO 3 , and even the extremely resistant Ascaris 

 lives only 5 to 6 hours in a 5.8% solution of this salt, LOE\V 

 ('77, p. 137) has found in Owen's Lake, California (an alkaline 

 water containing among other things 2.5% Na 2 CO 3 ), numerous 

 living Infusoria, Copepoda, larvae of Ephydra, and molds. 

 Again, the vinegar eel, Rhabditis aceti, lives in a 4% solution 

 of acetic acid, although this strength is usually fatal ; e.g. a 

 0.23% solution of acetic acid kills the tentacles of Drosera. 

 (DARWIN, '75, p. 191.) 



What is true of the whole organism is true also of its parts. 

 The gland cells of some marine Gasteropoda (Dolium, Cassis, 

 Tritonium, Natica heros) secrete H 2 SO 4 of a strength (2% to 

 3%) which is fatal to most protoplasm; the myriapod Foiitaria 

 excretes, when irritated, the extremely poisonous CHN; and, 

 according to LOEW ('87, p. 438), the plant Oxalis produces 

 potassic oxalate, which is a violent poison to most protoplasm. 



One general law of high resistance is worthy of notice: an 

 organism which produces an albuminoid poison is strongly 

 resistant to that poison. Thus, FAYRER ('74) has shown that 

 venomous serpents are not destroyed by the secretion of their 

 poison glands when it is injected into them ; and BOURNE 

 ('87) has shown that scorpions are not injured by their own 

 venom. 



An explanation of the facts of varied resistance capacity is 

 first gained through experiment. We all know that, among 

 men, a high resistance capacity to a poison may be acquired by 

 taking a small quantity of it at frequent intervals. Thus, 

 users of tobacco, alcohol, and various alkaloids become, in time, 

 capable of taking, without apparent injury, quantities which 

 would at first have proved fatal. Arsenic eaters may eventu- 

 ally swallow without injury four times the ordinarily lethal 

 dose, i.e. as much as 0.4 gramme. (BiNZ and SCHULZ, '79.) 



Results similar to those observed in man have been obtained 

 by experiment upon other animals. Thus, SEWALL ('87) 

 inoculated a pigeon hypodermically with sub-lethal doses of 



