1833.] The Variability of Protoplasm. 929 
experiments have been recently repeated by Dr. H. Valin, with 
results still more marked and surprising. 
To the conclusions as to the probable diversity of constitution 
in protoplasm, arrived at by the above-mentioned authors, may 
be added another, taken from a somewhat different point of view. 
There are physical as well as chemical reasons why certain ele- 
ments, and they only, are the main constituents of protoplasm. 
This may partly arise from their abundance and general diffusion, 
yet other elements which take nø part in the formation of proto- 
plasm exist abundantly in all parts of the earth. But we may 
note the additional fact that carbon, hydrogen, oxygen and nitro- 
gen are the only abundant elements which exist under conditions 
rendering active chemism possible. They all exist as gaseous 
constituents of our atmosphere, which contains no other element 
except in minute or local quantities. Two of them, oxygen and 
hydrogen, combine to form the only generally diffused liquid 
constituent of the earth. All other abundant elements exist as 
Solids, and usually in the state of oxide. 
Such is the general status of the chemical elements. All that 
are widely diffused, with the exception of atmospheric oxygen 
and nitrogen, exist as oxides. In consequence their chemical ac- 
tivity has nearly disappeared. At one period in the earth’s his- 
tory inorganic chemical action was probably very energetic. Now 
it has almost ceased to exist, through a general oxidation and 
solidification. Yet chemical activity has by no means ceased. 
Organic chemism has replaced inorganic. 
Modern physiological study has reduced to a simple formula 
the essential principles of organic chemistry. Certain of the 
Oxides are deoxidized. This is the basic principle of vegetable 
chemistry, The molecules thus produced are reoxidized. This 
is the characteristic feature of animal chemistry. A cycle of 
change is passed through, beginning with simple oxides and 
ending with the same simple oxides, while protoplasm forms the 
intermediate phase of the cycle. Vegetable chemistry consists 
Of a successive series of deoxidations, by which carbon and 
hydrogen are released more and more from the grasp of oxygen. 
The molecular result of these successive changes, compounded 
in some way with nitrogen, constitutes the basic molecule of 
Protoplasm. The exact method by which this is produced is not 
known. But it is known that in its production certain stable 
