MERCURIAL OINTMENT AND VAPOR OF MERCURY. 
57 
a liquid ; hence there would scarcely be any doubt « priori that 
this penetration is possible. It has already been shown by Beclard 
and Krause, that liquid mercury cannot penetrate the epidermis 
even when subjected to a perpendicular pressure of 26 inches ; 
but the extremely finely-divided state in which it exists in the 
ointment might possibly present a favorable condition for endos- 
mosis. Hence I first made some experiments with dead animal 
membranes. A pig's bladder was stretched over a vessel, and 
blue ointment rubbed upon it for a quarter, half, one, and even 
several hours ; the ointment never disappeared entirely, but there 
remained at last a tenacious bluish-gray layer on the surface. 
When the friction was concluded, the under side of the bladder 
was examined with the microscope ; and with a clean piece of 
gold. Globules of mercury can be readily detected under the mi- 
croscope in the form of spherical corpuscles, appearing perfectly 
black and opake by transmitted light, but exhibiting by reflected 
light a bright white and shining luminous spot. Gold is at least 
an equally delicate test from its power of forming an amalgam ; 
and a globule of mercury which is barely perceptible to the naked 
eye produces a distinct white spec upon a piece of gold. In the 
numerous experiments which were made, however, both methods 
always yielded a negative result ; neither in any case could a trace 
of the metal be detected between the coats of the bladder on strip- 
ping them off ; nor was a different result subsequently obtained, 
whether the friction was performed upon the porous or the mucous 
surface, or whether a dry or wetted bladder was used, or one im- 
pregnated with fatty matter. It was therefore repeated with the 
more delicate bladder of the calf and sheep ; and lastly, with the 
peritoneal coat of the liver of a calf, a membrane so thin that the 
smallest print can be read through it ; but in this case the piece 
of gold which had been enveloped in it did not exhibit any spot, 
nor did the microscope detect any globules. 
But the structure of the human skin and that of animals is dif- 
ferent from that of the serous and mucous membranes ; and it might 
be considered possible that the mercurial particles were rubbed 
into the orifices of the hair-cavities, the sebaceous and sudoriparous 
glands, and were thence taken up into the capillary vessels. But 
it is incorrect to imagine that the above organs are open canals ; 
