422 A Speculation on Protoplasm. ‘[July, 
of this fluid, the number of elements which essentially compose 
` it is few, thus: 
Water H; O 
AIDUMEH e s a C, H, N, O, S, slight variations in composition. Molecule 
Mucin C, H, N; O, variable. [not known. 
TGR ccs sled asin cba T N H, (CN) 
fens AO ae one C, H, N, O, 
Creatinine 5 
Sodium lactate.........Na, (G, H, O,) 
Fatty matters CoO; 0.013 to 0.12 p. c. per thousand. 
Glucose a on HH O; ; 
Mineral salts KCl NaCl CaCl, Na, CO; Na SO, K, SO, traces. 
Magacin an cece (ME (PON) Cay (POD Y ot w 07 P. c 
By glancing at the above tables it will be seen that the bulk of 
this fluid is made up of the type elements H! O" N™ C”, and 
these are essential, while sulphur, sodium, potassium, chlorine, 
magnesium, calcium and phosphorus are more or less accidental, 
or at least make up but a small part of its substance (z. e., 0.4 to 
I p. c. at the highest estimate). 
Even here, then, in a highly complex animal fluid, one about 
to commence the architecture of the various parts of one of the 
most complex animals in nature—man; the bricks, though most 
diverse in form, color and durability, are almost altogether com- 
posed of the same four simple substances which make the waters, 
the atmosphere and the plants, viz: C N O H 
But this conformity to rule, which would mal these elements 
the only four necessary constituents of organisms, though close, 
is not exact. Sulphur always occurs, though in small and vary- 
ing quantity. Phosphorus is generally present as an inorganic 
compound. 
~ Nor is it Sie (1) how greatly this material may vary in 
constitution and still subserve the needs of the growing thing 
which assimilates it; (2) how greatly the needs themselves of a 
race of growing things may alter with gradually changing cir- 
cumstances, Has it always been necessary to build living things 
out of three combustibles and a diluent? When one attempts to 
speculate upon the possible answers to these now unanswerable 
questions, the difficulties crowd thick upon him. In the early 
history of the universe (or better, of our own planetary family) 
was it possible for living beings to exist? What constitutes & 
living being? Some physiologists hold nutrition and reproduc- - 
