PROFESSOR GRAHAM ON OSMOTIC FORCE. 
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seen to possess a singular influence in diminishing the positive osmose of the last- 
named alkaline salt; while a mixture of small proportions of common salt and 
hydrochloric acid exhibits, with the membrane in certain conditions, an intense 
positive osmose which neither of these substances possess individually. 
The bibasic salts of potash again, such as the sulphate and oxalate, although strictly 
neutral in reaction, begin to exhibit a positive osmotic power, in consequence, it may 
be supposed, of their resolvability into an acid salt and free alkaline base. 
The sulphate of potash, when strictly neutral, has in different membranes a variable 
but always moderate positive osmose, an osmose which the slightest trace of a strong 
acid may cause to disappear entirely, or even convert into a small negative osmose. 
On the other hand, a minute addition of an alkaline carbonate to the sulphate of 
potash appears to give that salt a positive osmose of a high order, ft was seen that 
the mixed salts produce much more osmose than the sum of the osmose of the two 
salts used apart from each other. 
This property of sulphate of potash must wait for its explanation, with many other 
facts of the subject, till fuller information is obtained than I can at present offer re- 
specting the nature of the obscure chemical changes which occur in the membrane 
during osmose, and of the mode in which masses of water come to participate in these 
changes. The conclusion which has been drawn, that the osmose or movement of 
water through membrane is always towards the side of the base, is no theory or 
explanation of the phenomenon, but a general description, which appears to apply 
with sufficient accuracy to all the observations. 
It may appear to some that the chemical character which has been assigned to 
osmose takes away from the physiological interest of the subject, in so far as the 
decomposition of the membrane may appear to be incompatible with vital condi- 
tions, and osmotic movement confined therefore to dead matter. But such appre- 
hensions are, it is believed, groundless, or at all events premature. All parts of living 
structures are allowed to be in a state of incessant change, — of decomposition and 
renewal. The decomposition occurring in a living membrane, while effecting osmotic 
propulsion, may possibly therefore be of a reparable kind. In other respects chemical 
osmose appears to be an agency particularly well adapted to take part in the animal 
ceconomy. It is seen that osmose is peculiarly excited by dilute saline solutions, 
such as the animal juices really are, and that the alkaline or acid property which 
these fluids always possess is another most favourable condition for their action on 
membrane. The natural excitation of osmose in the substance of the membranes or 
cell-walls dividing such fluids seems therefore almost inevitable. 
In osmose there is, further, a remarkably direct substitution of one of the great 
forces of nature by its equivalent in another force — the conversion, as it may be said, 
of chemical affinity into mechanical power. Now, what is more wanted in the theory 
of animal functions than a mechanism for obtaining motive power from chemical 
decomposition as it occurs in the tissues ? In minute microscopic cells the osmotic 
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