ON THE PHYSIOLOGICAL ACTION OF MEDICINES. 27 
oxides. It is insoluble in water, but soluble in alcohol with a yellow colour. 
- It therefore resembles the resins in its general properties. It cannot be ob- 
_ tained in a crystallized state. From a hot concentrated solution in alcohol 
__ it separates on cooling as a yellow powder. It imparts no colour to mor- 
danted cloth. 
On the Physiological Action of Medicines. By J. Buaxn, M.B., F.R.C.S. 
- Tue present report is a continuation of those which have already been read 
before this section, and which have been published in the reports of the 
Association. The only additional experiments I now have to bring forward 
have been instituted to investigate the action of the salts of iridium and 
osmium, and the acids of selenium and sulphur, when introduced directly 
into the blood. 
' The experiments that have been made with the salts of iridium and osmium 
prove that these substances closely agree in their physiological action with 
the salts of palladium and platinum. They are, like these salts, very poison- 
ous. A solution containing half a grain of the double chloride of iridium 
and ammonia, was injected into the jugular vein of a dog. Before the injec- 
q _ tion, the action of the heart was regular and strong*; in eight seconds after 
the injection, the action of the heart appeared affected, it being rendered flut- 
tering; and after a few seconds there was an apparent obstacle to the passage 
of the blood through the systemic capillaries, as the pressure in the arterial 
system became greater. In about a minute the pressure again diminished ; 
_ the action of the heart was slower, the force it exerted in propelling the blood 
being equal to a column of mercury of but three inches and a half, or little 
more than the half of that under which the circulation is generally carried 
on. The animal appeared to be uncomfortable, owing to the circulation be- 
_ coming so feeble. On injecting a solution containing a grain of the salt, the 
circulation was arrested in eleven seconds, owing either to the action of the 
heart having ceased, or else that its contractions were so weakened that they 
did not suffice to force the blood through the pulmonary capillaries. The 
‘pressure exerted by the blood in the arterial system became suddenly dimi- 
a nished, so as only to support a column of mercury of an inch and a half, at 
_ which point the circulation through the capillaries would appear to have 
been suspended, for the pressure remained stationary for more than a minute, 
' and then sunk to zero, owing to relaxation of the capillaries taking place. 
~ Death followed about three minutes and a half after the injection, and the 
__eye retained its sensibility to mechanical irritation for three minutes; respi- 
_ ration and sensibility continuing nearly two minutes longer than would have 
__ been the case had the injection of the salt totally paralyzed the heart. On 
Opening the thorax immediately after death, the heart was found contracting 
_ tythmically, but very feebly, certainly not with sufficient power to propel its 
contents: both cavities were full of blood; in the right it was dark, that in 
the left was of a maroon colour, and had evidently been oxygenized, proving 
that the circulation had ceased before respiration was suspended. The blood 
__ eoagulated imperfectly, and this has been noticed after the introduction of 
s the salts of palladium and platinum, which are isomorphous with those of 
ui 
aia * The state of the circulation is ascertained by the hemadynamometer, an instrument which 
enables us readily to detect any change in the action of the heart or in the passage of the 
