565 
was noted ; it varied from half an hour to one hour and a quarter. 
The whole body was immersed, excepting the head and neck. All 
the urine voided in twenty-four hours after each bath was collected 
and concentrated, then tested for the substances experimented on. 
Six baths were taken, in which iodide of potassium was dissolved. 
The quantity of the salt varied from 200 to 1300 grains. 
Five baths, in which quantities of ferrocyanide of potassium, va- 
rying from 1400 to 5000 grains, were dissolved. Four baths were 
taken, the water of which was rendered strongly alkaline by soda. 
The result of these fifteen experiments was, that I could not find 
that any of the substances in the baths passed through the skin into 
the blood, so as to be found in the urine ; the soda baths did not ren- 
der it alkaline, nor could I detect the other salts in it ; and it is to 
be noted that the tests for them are extremely delicate. 
To compare absorption from a mucous surface with the above, I 
swallowed several different quantities of iodide and ferrocyanide of 
potassium, when I found that the smallest amount of the former 
salt I could take internally, and afterwards detect in the urine, was 
two grains, and of the latter five grains. 
A considerable number of trials were made in which tincture of 
iodine, and two in which iodine ointment were applied to the skin. 
Neither in these could I afterwards find iodine in the urine. 
The general conclusion which my experiments lead me to are, (1.) 
That though not denying that absorption by the skin of aqueous 
solution does take place, yet it seems to be the exception and not 
the rule. (2.) That medicated warm baths, whether natural or arti- 
ficial, do not appear to owe any virtue they may have to the sub- 
stances dissolved in them reaching the blood through the skin. At 
the same time, as there are other ways by which one can conceive 
such baths to operate on the system, it is not to be concluded that, 
because absorption may not take place, such baths are useless as 
therapeutic agents. 
4. On the Constitution of Mannite. By J. A. Wanklyn, Esq., 
and Dr Erlenmeyer. 
Chemists are in the habit of assigning to mannite the formula, 
c 6 h 14 o 6 ; 
hut the reasons which have hitherto been given for that formula 
