268 CAUSES OF VARIATION 



Nageli's experiments : indicate that water distilled in cop- 

 per vessels, or standing four days in other vessels with twelve 

 clean copper coins per each liter of water, was fatal to Spiro- 

 gyra, though the proportion of copper to water was but i to 

 77,000,000. 



These reactions, resulting in death rather than in modified 

 action, are important, not as showing primary causes of varia- 

 bility but as proving again that living protoplasm is still subject 

 to many of the chemical affinities that controlled its elements 

 before they became organized into living matter. It must be 

 remembered in this connection that many of these substances 

 attack only living protoplasm, having no action upon dead pro- 

 toplasm, showing that at death the highly complex materials 

 have, to some extent at least, broken down. 



The action of some poisons, like nicotin, is proportional to 

 the " differentiation of nervous substance " ; others, like cocain 

 and atropin, first excite and then paralyze the central nervous 

 system of vertebrates, but act as violent poisons upon undiffer- 

 entiated protoplasm (Protozoa). 2 



Toxic poisons. It is not the germ that kills, but rather its 

 specific toxin that deranges some of the vital functions beyond 

 endurance. The dire effects of germ diseases are therefore due 

 not so much to the organisms themselves as to their constant 

 manufacture within the body of a chemical poison which the 

 protoplasm cannot endure and preserve its normal functions. It 

 may die in the attempt, or it may succeed and become accli- 

 mated, but while the struggle is on, the body functions will be 

 considerably disturbed. It is significant that compounds similar 

 to those of disease-producing bacteria have been " extracted from 

 the seeds of some phanerogams ; for example, ricin from the seeds 

 of the castor-oil bean, etc." In this class may come the poisons 

 secreted by certain animals, as the rattlesnake and cobra, fatal 

 to vertebrates but innocuous to Infusoria and Flagellata. 



It is also noteworthy that the blood serum of one species 

 rapidly dissolves the corpuscles of another (red and white), and 

 is therefore injurious or fatal according to the amounts present. 3 



1 C. I*. Davenport, Experimental Morphology, Part I, p. 14. 



2 Ibid. pp. 23 and 24. 3 ibid. p. 22. 



