EXTERNAL INFLUENCES AS CAUSES OF VARIATION 267 



" the poisonous action increases up to a certain limit in proportion 

 to the number of C atoms" while " above this limit the com- 

 pounds are more stable and are more indifferent, as for example 

 paraffin (C 21 H 44 to C 27 H 56 ).". 



Again, in such a series, if the H atoms become replaced by 

 one of the halogens, the poisonous properties correspondingly 

 increase ; thus : * 



CH 4 , marsh gas, innocuous. 



CH 3 C1, slightly anaesthetic. 



CHC1 3 , chloroform, powerful anaesthetic. 



CC1 4 , very dangerous, stupefying involuntary muscles. 



Chloroform and etber affect all protoplasm, both plant and 

 animal, higher as well as lower. They seem to produce at first 

 (two to five minutes in a 25 per cent water solution) a " very 

 intense excitement in the movement of the protoplasm," fol- 

 lowed by " strong vacuolization, and then the cytoplasm grad- 

 ually becomes immobile " and dies, if the influence is continued. 

 In a similar way the various alcohols exert stupefying effects in 

 proportion to the number of CH 2 radicals present, and carbon 

 disulphid (CS 2 ) is one of the most powerful catalytic poisons. 



OProtoplasm is therefore subject to catalytic disturbances, in 

 which it is not different from other and more ordinary chemical 

 materials, a fact in itself exceedingly significant to the stu- 

 dent looking for fundamental causes of variation. 



Poisons which form salts. 2 These are acids and bases which 

 Loew believes, as stated by Davenport, "unite [directly] with 

 the protein substances of the protoplasm, producing salts," 

 disturbances that of course soon lead to death. Thus " formic 

 acid, even in small per cents, 0.05 per cent to 0.006 per cent, 

 prevents the development of bacteria. On the other hand, 

 some protoplasm has acquired a resistance to organic acids, the 

 vinegar eel living in 4 per cent acetic acid," and the gland cells 

 of some marine Gastropoda secrete from 2 per cent to 3 per 

 cent of H 2 SO 4 , a strength which is fatal to most protoplasm. 



1 The halogens fluorin, chlorin, bromin, and iodin form a group of sub- 

 stances of very similar chemical properties, but form, in the order named, a 

 decreasing series as to chemical energy. 



2 C. B. Davenport, Experimental Morphology, Part I, pp. 12-14. 



