8·6 × 32 × 10−22 mgm. = 275 × 10−22 mgm.
The analysis of ordinary bacteria shews them to consist[69] of about 85% of water, and 15% of solids; while the solid residue of vegetable protoplasm contains about one part in a thousand of sulphur. We may assume, therefore, that the living protoplasm contains about
1⁄1000 × 15⁄100 = 15 × 10−5
parts of sulphur, taking the total weight as = 1.
But our little micrococcus, of 0·15 µ in diameter, would, if it were spherical, have a volume of
π⁄6 × 0·153 µ = 18 × 10−4 cubic microns; {41}
and therefore (taking its density as equal to that of water), a weight of
18 × 10−4 × 10−9 = 18 × 10−13 mgm.
But of this total weight, the sulphur represents only
18 × 10−13 × 15 × 10−5 = 27 × 10−17 mgm.