1908-9. ] ON THE ORIGIN OF LIFE ON THE GLOBE. 431 
simplicity, endowed like existing fungi with power of determining the 
formation of new protoplasins from such matters as ammonium carbon- 
ates, oxalates and tartrates, alkaline and earthy phosphates and water 
without the aid of light.” 
The greatest difficulty experienced in attempting to account for 
the origin of life on the globe as a result of physical and chemical con- 
ditions has always been found in the complexity of the molecules of the 
proteins which enter into the composition of protoplasm, the physical 
basis of life. Forty, thirty, and even ten years ago the constitution of 
protein seemed an insoluble riddle. Proteins are undoubtedly the most 
complicated compounds known to the chemist. The latter has been 
able to determine the composition of as many as one hundred thousand 
organic compounds, that is, apart from proteins, the whole range of 
organic compounds, but he was unable till recently not only to 
synthesize the simplest protein derivatives but also to have even 
a faint conception of what atom groups the protein molecule is com- 
posed. 
The work of Kossel and his school gave the first light on the 
problem. By means of hydrolysis with dilute mineral acids the protein 
molecule was shown fo be largely constituted of amino acids, acids in 
the majority of cases belonging to the “fatty” series with one of the 
hydrogens of one or more alkyl groups replaced by NH, and thus giv- 
ing bodies each of which is at the same time both an acid and a base. 
The simplest of these amino-acids is known as amino-acetic acid which 
is constituted thus :— 
CH, (NH),. COOH 
This is one of the most abundant constituent atom-groups of the 
molecule of gelatine. The next higher amino-acid is 4-amino-propionic 
acid which is commonly called alanine and which has the following 
constitution :— 
CH, CH(NH,) COOH 
There are a large number of others, the more important of which 
are cysteine or 4-amino-/-thio-propionic acid :— 
GH(sit). CHi(NH.) COOH: 
Valine or a-amino- isovalerianic acid, 
CH; 
ee CH. CH(NH,). COOH: 
