ANALOGY. 97 



digestion, and that the glands absorb the 

 digested matter." 1 "These are, perhaps, the 

 most interesting of all my observations on 

 Drosera, as no such power was before distinctly 

 known to exist in the vegetable kingdom." 

 Having by analogy established the power of 

 true digestion in plants, analogy led him to 

 seek in plants the elements that do the work 

 of digestion in animals. Bringing together 

 what was known of plants, he pointed out that 

 the juices of many plants contain an acid, and 

 so one element of a digestive fluid was at hand; 

 and that all plants possess the power of dis- 

 solving albuminous or proteid substances, pro- 

 toplasm, chlorophyll, etc., and that "this must 

 be effected by a solvent, probably consisting 

 of a ferment together with an acid." 2 After 

 writing the last quoted sentence he learned 

 that a ferment which converted albuminous sub- 

 stances into true peptones had been extracted 

 from the seeds of the vetch. 



Sachs mentioned the discovery of the fer- 

 ment, recorded the fact that peptones had 

 themselves been actually found in the seeds of 

 the lupine, and added "as we come to know 

 the proteinaceous reserve materials of plants 

 better, and if we follow their behavior in the 



1 Insectivorous Plants, p. 268. 2 Ibid., p. 362. 



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