1883.] Physiology. 561 
as the height of the fluid column. Hence he infers that the 
sound comes from the fluid and not from the membrane. Further, 
that as the membrane is subjected to unequal pressure on its op- 
posite sides, is in fact distended by the weight of the water, it is 
not able to produce sonorous vibrations. He then concludes that 
the second sound of the heart, which is produced by the impact 
of a fluid column, the arterial blood, against membranous septa, 
the semilunar valves, originates in the vibration of the blood, and 
not of the valves.” 
On repeating these experiments by a modified method, C. E. 
Webster concludes that the second sound of the heart is the 
combined result of the vibrations both of the fluid blood column 
and of the membranous semilunar valves.—/ourn. of Physiology, 
Vol. ttt, p. 294. 
A SIMPLE METHOD OF DEMONSTRATING THE ALKALINE REAC- 
TION OF THE BLoop.—A drop of blood, obtained by pricking the 
finger, is placed upon the smooth colored surface of a piece of 
the dry, faintly reddened, g/azed, litmus paper, and after a few 
seconds is wiped off with the corner of a handkerchief or clean 
linen rag moistened with water. The place where the blood has 
Stood is seen to be marked out as a well-defined blue patch upon 
the red or violet ground. Nothing can be clearer or more con- 
vincing than the demonstration of the natural alkalinity of the 
blood which is afforded by this simple experiment —E£. A. Schäfer, 
Journ. of Physiology, Vol. iti, p. 292. 
INFLUENCE oF LicuT upon BacTerta.—Th. W. Engelmann de- 
Scribes a new form of Bacterium, called by him 2. photometricum, 
which exhibits some remarkable reactions toward light. This 
erium moves only when illuminated, coming to a state of rest 
ik “hn according as it is removed from or is brought into the 
gat, 
5 Access of oxygen is favorable and probably necessary to mo- 
tion, but the gas has not the stimulating effect of sunlight. The 
rapidity of movement increases proportionately with the intensity . 
of illumination, and motion gradually ceases on removal from 
ne light. Long continued action of very strong light, especially 
when little oxygen is present, brings the Bacteria to rest. Sud- 
den diminution in the intensity of illumination produces remark- 
able agitation, such as rapid rotary movements. When the field 
9f the microscope is partially shaded the Bacteria are seen to 
was greater or less respectively as the supply of oxygen was 
_ diminished or increased. a 
| When the field of the microscope is illuminated by pure spec- 
eal colors, most of the Bacteria wander into the region of the 
red 
-Ted rays where they are heaped in a narrow, sharply bounded 
