ORGANIZATION OF THE BACTERIA. 37 
Cohn has first pointed out the movements of the 
protoplasm, in which currents occur, above all in 
the central portion, the peripheral portion remain- 
ing homogeneous and motionless. The vacuoles 
are also found in the central portion; Warming, 
however, who has observed them in Jonas Okenii, 
Vibrio rugula, V. serpens and Spirilum undula 
var. littoreum, has sometimes seen them in the mid- 
dle of the plasma, at another near the exterior wall. 
The granules which are seen in the protoplasm 
were considered by Ehrenberg as stomachal vesi- 
cles or ovules. They are of two sorts; the one, 
highly refractive and not bordered by a dark circle, 
are considered by Warming as nothing more than 
mere compact masses of protoplasm; the second, 
also highly refractive, but surrounded by a dark 
circle, resemble drops of oil, and have been taken 
for fat granules; but the recent researches of 
Cramer, Cohn, and Warming have proved that 
some of them, at least, are formed of crystalline 
sulphur. They are not soluble either i hydro- 
chlorie acid or in water, but they are dissolved in 
absolute alcohol, in hot caustic potash and sulphite 
of soda, in nitric acid and chlorate of potash at 
ordinary temperatures, and in bisulphide of carbon, 
when the membrane, which is permeable with dif- 
ficulty, has been previously destroyed by sulphuric 
acid. Although their small dimensions and great 
refractive power prevent them from being dis- 
tinguished with certainty as crystals of sulphur, as 
they are doubly refractive to polarized light their 
crystalline nature cannot be doubted. 
