SCIENCE LETTER FROM FRANCE. “7 
of the contraction executed, but none in point of view physiological. From the 
moment there is no external work, there is no consumption of heat; when a 
muscle contracts, there is a diminution of temperature, and deoxidation. Fol- 
lowing the contraction or expansion of the muscles, the physiological actions will 
vary: a Swiss guide will ascend a mountain, carrying a burden, without mani- 
festing fatigue; but perspiration will be more or less intense; the pulse and 
respiration will be accelerated; the panting will be more or less sensible, following 
the robustness of the individual. These phenomena will be less during the descent. 
Does intellectual work consume or produce heat? No, according to M. Hirn, 
the course of our thoughts modify at each moment the march of the organic 
functions ; each feeling of joy, of sadness, of pain, of fear, or of agony, determines 
special modifications in the rythms of the pulse, of respiration, etc.; nervous 
persons know how each emotion may create muscular tremblings, and active 
heart-beatings; intense and sustained intellectual work often produces cutaneous 
transpiration, amounting to positive perspiration. Is there no loss of heat in this 
case? None, because the labor is internal, and has nothing in common with 
external manual work; but the intellectual exertion can influence the nature of 
the materials that oxygen burns, during the process of respiration; it can modify 
the employment of oxygen, and thus change the conditions of combustion. 
M. de Bellesme has been studying the phosphoresence of the glow-worm, 
from the physiological side; he substituted for the will of the insect, an electric 
current, and was thus enabled to produce the luminousness desired. He ascer- 
tained, and so corroborates Matteucci, that the presence of oxygen is indispensable 
to the production of phosphoresence, hence, there is in the luminous organ the 
production of a matter, which, in combination with the oxygen of the air, produces 
light; the structure of that organ excludes the possibility of all secretion, liquid 
or solid, for the matter is gaseous, and only phosphuretted hydrogen is glowing 
under ordinary conditions. Not only is there no phosphorus accumulated in the 
organ, but there is no provision of matter at all. M. de Bellesme has demon- 
strated conclusively, that the luminous substance is produced in proportion as 
it is required—never accumulated; that phosphorescence is a general property of 
the protoplasma, the result of phosphuretted hydrogen produced therein by chem- 
ical decompositions in connection with the cellules of the organ; the decomposi- 
. tion in the case of the glow-worm, being under the nervous influence of the insect, 
and which is essential for setting free the phosphorescence. 
The estimation of the quantity of cream contained in milk can now be made 
very accurately and rapidly, by means of centrifugal force. Attach the handle 
of a can, filled with milk, toa cord; hold the other extremity of the latter in 
the hand, and twirl as if for a sling; the cream, lighter than the rest of the milk, 
will accumulate on the surface free from all liquid, and more quickly than if in a 
state of repose; the time will even be lessened in proportion as the revolutions 
are rapid. When the milk has a temperature of 59 to 68 degrees F., the separa- 
tion of the cream takes place in fifteen minutes, at the rate of 600 revolutions per 
