PRIMARY STAGES OF LIFE 67 



of a bird, the Turaco. Although among the rare Hfe elements 

 it ranks first in toxic action upon fungi, algse, and in general 

 upon all plants, yet it is occasionally found in the tissues of 

 trees growing in copper-ore regions.^ 



In general most of the metallic compounds and several of 

 the non-metallic compounds are toxic or destructive to life 

 when present in large quantities. All the mineral elements of 

 high atomic weight are toxic in comparatively minute propor- 

 tions, while the essential life elements of low atomic weight 

 are toxic only in comparatively large proportions. Toxicity 

 depends largely upon the liberation of ions, and non-ionized 

 and non-ionizable organic compounds — such as hemoglobin 

 containing non-ionizable iron — are wholly non-toxic. 



Pure Speculation as to the Primary Physicochemical 



Stages of Life 



The mode of the origin of life is a matter of pure specula- 

 tion, in which we have as yet little observation or uniformitarian 

 reasoning to guide us, for all the experiments of Biitschli and 

 others to imitate the original life process have proved fruitless. 

 We shall, however, from our knowledge of bacteria (see Chap. 

 Ill) put forward five hypotheses in regard to it, considering 

 the life process as probably a gradual one, marked by short leaps 

 or accessions of energy, and not as a sudden one. 



First: We may advance the hypothesis that an early step 

 in the organization of living matter was the assemblage one by 

 one of sev^eral of the ten elements now essential to life, namely, 

 hydrogen, oxygen, nitrogen, carbon, phosphorus, sulphur, po- 

 tassium, calcium, magnesium, and iron (also perhaps silicon), 

 which are present in all living organisms, with the exception 

 of some of the most primitive forms of bacteria which may 



' M. A. Howe, letter of February 24, 1916. 



