Bladder was tied over the necks of three wide-mouthed vials, with bottoms cut off, and each was filled with iodide of potassium ointment.

No. 1 contained an ointment made with lard.

No. 2, one made with unguentum paraffini (Germ.  Pharm.), and

No. 3, one made with unguentum paraffini mixed with 3 per cent. of lard.

All three vials were then suspended in beakers filled with water.  After standing twenty-four hours at the ordinary temperature, the contents of none of the beakers gave any iodine reaction.  After having been placed into a warm temperature, between 25-37 deg.  C., all three showed iodine reactions after three hours, Nos. 2 and 3 very strongly, No. 1 (with lard alone) very faintly.

The same experiment was now repeated, with the precaution that the bladder was previously washed completely free from chlorine.  Each vial was suspended, at a temperature of 25-27 deg.  C., in 50 grammes of distilled water.  After three hours, the contents of No. 1 (containing the ointment made with lard) gave no iodine reaction; the contents of the other two, however, gave traces.  After eight hours no further change had taken place.  The temperature was now raised to 30-35 deg.  C., and kept so for eight hours.  All three beakers now gave a strong iodine reaction, 0.2 c.c. of normal silver solution being required for each 15 grammes of the contents of the beakers.

In addition to the iodide, some of the fatty base had osmosed through the membrane in each case.

The next experiment was made by substituting a piece of the skin (freed from chlorine by washing) of a freshly killed sheep for the bladder.  The ointment in No. 3 in this case was made with 10 per cent. of lard.  No reaction was obtained, at the ordinary temperature, after twelve hours, nor after eight more hours, at a temperature of 25-30 deg.  C. After letting them stand for eight hours longer at 30-37 deg.  C., a faint reaction was obtained in the case of the ointment made with unguentum paraffini; a still fainter with No. 3; but no reaction at all with No. 1 (that made with lard).  None of the fats passed through by osmosis.  After eight hours more, the iodine reaction was quite decisive in all cases, but no fat had passed through even now.  On titrating 20 grammes of the contents of each beaker,

No. 1 required 0.5 c.c. of silver solution. 
No. 3    "     0.5 c.c.         "
No. 2    "     0.7 c.c.         "

showing that the most iodine had osmosed in the case of the ointment made with unguentum paraffini (equivalent to vaseline).

* * * * *

THE TAILS OF COMETS.

I.—­If we throw a stone into the water, a wave will be produced that will extend in a circle.  The size of this wave and the velocity with which it extends depend upon the size of the stone, that is to say, upon the intensity of the mechanical action that created it.  The extent and depth of the water are likewise factors.