Royal Society. 483 
As the fluids contained in the vessels and in the cells hold in so- 
lution various vegetable compounds, their density is greater than 
the ascending sap, which is external to them, and from which they 
are separated by an intervening organized membrane. Such being 
the conditions requisite for the operation of the principle of endos- 
mose, the author infers that such a principle is constantly in action 
in living plants; and that it is the cause of the continual trans- 
mission of fluids from the intervascular and intercellular spaces 
into the interior of the vessels and cells, and also of the ascent of the 
sap. 
Dec. 22.—A paper was in part read, entitled “On the Nerves :” 
by James Stark, M.D., F.R.S.E. Communicated by James F. W. 
Johnston, Esq., F.R.S., Professor of Chemistry in the University of 
Durham. 
Jan. 12, 1843.—1. The reading of a paper, entitled “On the 
Nerves,” by James Stark, M.D., was resumed and concluded. 
The author gives the results of his examinations, both microscopical 
and chemical, of the structure and composition of the nerves; and 
concludes that they consist, in their whole extent, of a congeries of 
membranous tubes, cylindrical in their form, placed parallel to one 
another, and united into fasciculi of various sizes ; but that neither 
these fasciculi nor the individual tubes are enveloped by any fila- 
mentous tissue; that these tubular membranes are composed of 
extremely minute filaments, placed in a strictly longitudinal direc- 
tion, in exact parallelism with each other, and consisting of granules 
of the same kind as those which form the basis of all the solid 
structures of the body; and that the matter which fills the tubes 
is of an oily nature, differing in no essential respect from butter, 
or soft fat; and remaining of a fluid consistence during the life of 
the animal, or while it retains its natural temperature, but becoming 
granular or solid when the animal dies, or its temperature is much 
reduced. As oily substances are well known to be non-conductors 
of electricity, and as the nerves have been shown by the experiments 
of Bischoff to be among the worst possible conductors of this agent, 
the author contends that the nervous agency can be neither elec- 
tricity, nor galvanism, nor any property related to those powers; 
and conceives that the phenomena are best explained on the hypo- 
thesis of undulations or vibrations propagated along the course of 
the tubes which compose the nerves, by the medium of the oily 
globules they contain. He traces the operation of the various 
causes which produce sensation, in giving rise to these undulations ; 
and extends the same explanation to the phenomena of voluntary 
motion, as consisting in undulations, commencing in the brain, as 
determined by the will, and propagated to the muscles. He corro- 
borates his views by ascribing the effects of cold in diminishing or 
destroying both sensibility and the power of voluntary motion, par- 
ticularly as exemplified in the hybernation of animals, to its mecha- 
nical operation of diminishing the fluidity, or producing solidity, in 
the oily medium by which these powers are exercised. 
2. A letter from Prof. Hansen to G. B. Airy, Esq., F.R.S., A.R., 
2K2 
