and 8 to the same cause? Let us take the simple fact, that, when the mucous membrane of the small intestine and the blood flowing from it are formed into a circuit, a deviation of the needle amounting to 3°, 4° or 5° is obtained, the intestine being empty and therefore uninfluenced by the circumstances we have just now mentioned; why did the effect not occur in experiment 11? the conditions appeared to be precisely similar; or in experiments 7 and 10, when the artery was wounded; or in experiments 3 and 4, when blood flowing from a different part formed the circuit; or in experiments 3, 5, 9, when a circuit was formed between the inside and outside of the gut? Did not the failure arise in these instances in consequence of the absence of one necessary condition, the flowing of the blood from the same part, the transmission of the carrying particles from one electrode to the other, as shown in experiments 2, 3, 4, 5 and 7?

Without entering into any discussion as to the mode in which the effect may be supposed to be brought about in the living animal, and the difference observed when the stomach and other parts were formed into circuits in rabbits, and when the same circuits were formed in cats, we may be justified in adding the following to our former inference, viz. that the effect is produced during the organic action of the part, it ceasing after the death of the animal.

Instead of endeavouring to refute the notion that the stomach and liver form poles similar to those of a galvanic circle, let us briefly allude to the experiment and conjecture of WOLLASTON. Was not that experiment to illustrate, rather than to prove his conjecture? and are not these experiments identical with that conjecture? He evidently saw, mentally speaking, the meaning of that phrase "AN AXIS OF POWER," &c. This inquiry has been undertaken with the advantage both of FARADAY'S labours and the use of the galvanometer. WOLLASTON'S conjecture and experiment have existed for forty years.

The following is a brief recapitulation of the general conclusions which may be deduced from the foregoing experiments and reasonings :

1. When the electrodes of a galvanometer are brought into communication, one with the mucous membrane of the alimentary canal, the other with the blood flowing from the same part, a deviation of the needle takes place, indicating that the secreted product and the blood are in opposite electric states.

2. That the effect occurs during the life of the animal, it ceasing after its death. 3. That the effect may be considered as arising from the decomposition of the blood; i. e. the changes which occur during the formation of the secreted product and venous blood.

4. That these changes are effected by the organic action of the part.

The author begs to acknowledge the great kindness that he has received from Sir B. C. BRODIE, Bart., and from Dr. TODD.

12 New Burlington Street.

EXPLANATION OF THE WOODCUT.

Fig. 1. Wooden mercurial cup.

Fig. 2. Copper wire to form the communication between the galvanometer and

mercury.

Fig. 3. A section of the mercurial cup, showing the mode in which the thick copper wire was connected with it.

Fig. 4. Shows the manner in which the plate of platinum was soldered on to the platinum electrode, pure gold being used; all the part within the dotted line, and for a short distance up the wire, was coated with shell-lac to prevent the action of the mercury upon it.

Fig. 5. Electrode A.

Fig. 6. Electrode B.

Fig. 7. Electrode C. Fig. 8. The arrangement with the galvanometer previous to each experiment. Fig. 9. a a a, arteries; b b b, veins; the arrows indicate the course of the blood: c, point of the electrode in contact with the wounded vein; the dotted line of d the electrode in contact with the mucous surface of the small intestine.

XVIII. On the Direction assumed by Plants. By Professor MACAIRE of Geneva. Communicated by P. M. ROGET, M.D., Sec. R.S.

Received June 17,-Read June 17, 1847.

§ 1. On the Curling-up of Tendrils.

THE plants with tendrils are very numerous. According to Mr. PALM there are about five hundred, divided into seventeen families. Of these, one hundred and sixty have a ligneous stem, eighty-three are perennial herbs, and one hundred and seventeen are annuals.

My experiments on the mode of curling-up of these organs were made on the tendrils of the Tamus communis*, a plant of the family of the Asparageæ. The tendrils of this plant seem to be a thread-like degeneration of the footstalk of a leaf, whose place they occupy on the stem of the plant. They are at first straight, and are implanted perpendicularly on the stem, so as to form almost a right angle with it; the extreme end of the tendril only has a slight tendency to bend towards the stem. When the tendril of the Tamus is touched by any solid body whatever on a point of its surface not too far from the extremity, it contracts itself from the outside inwards, forming at first a hook and then a curl, so as to embrace the body closely if that body be circular; if angular, the knot is only tight on the angles, and bulges out on the surfaces. When a first knot is tied, the end of the tendril continues to roll itself up in a coil, though not in contact with the body in that part, and the coil slides over the external object, coming nearer and nearer to it so as to embrace it several times: in the mean while, the other end of the tendril continues also to contract itself. In this way as many as seven or eight knots are formed. I have frequently seen three tied before my eyes within the space of a quarter of an hour on a metallic wire, small branches of wood, a pencil, my finger, &c. The contact of any solid body whatever is sufficient to produce this effect; so much so, that although the tendril is evidently destined by nature to support the creeper to which it belongs, by means of the surrounding plants, yet if it chances to meet a part of the very same plant of Tamus of which it is itself a portion, the contact causes it immediately to roll itself that portion.

up around

* Since this paper was read the author has been informed that Tamus communis is a plant without tendrils. The plant on which he made the experiments here referred to is a common weed in the gardens in Switzerland. Being without the means in this country of identifying it, he must supply the information on a future occasion, only adding that Smilar aspera, another of the Asparageæ, has been suggested to him as being probably the plant.

The tendril of the Tamus is very smooth, and its surface contains neither resinous nor glutinous matter, nor hair of any kind. When slightly rubbed between the fingers, it does not contract itself. To obtain its curling up, it is necessary that the contact should be only on one side. If the solid body round which the tendril had begun to coil be removed, it continues to contract itself in the air, but without fastening the knot on itself, the empty ring remaining constantly open. If, after a little time, an object of suitable size and form be introduced in this empty ring, it contracts anew and the knots tie themselves firmly on this new body.

If the tendril be left without internal support after its contraction, it does not turn again, nor resume its primitive direction in a straight line; on the contrary, the contractions are soon extended over the whole of the tendril so as to give it the appearance of a corkscrew.

The same thing happens to those tendrils the extremities of which are attached to a supporting body. This arrangement has the effect of preventing the tearing of the tendril when the plant is shaken by the wind, by giving it the shape and elastic properties of an helicoidal spring (ressort à boudin). I placed a small portion of a branch in contact with a tendril of Tamus; when it had begun to contract itself and the first knot had been tied, I let the branch go and it remained suspended. Not only did the tendril support the weight of the branch, but it continued to roll itself up around it, raising it more and more by each knot. Ten rings were thus formed around the slip, regularly arranged in a spiral by the side of each other. The branch was entirely covered over by them, and as there was no room for more, the tendril continued to contract itself in the air towards its base, and to form empty rings in the form of a corkscrew, having nearly the same dimensions as those on the branch.

When a body, such as an iron rod, too heavy to be supported, is placed in this way, the knot formed becomes loose and the rod drops. If the tendril rolls itself round a body that is soft and not elastic, such as a piece of packthread, it presses it tightly enough to render its diameter visibly less in the part where the knots are tied. This pressure may even be rendered sensible to the touch if the knot be suffered to form round the finger, and it goes on increasing to a certain extent.

When the tendril lays hold of an elastic body having a conical shape, such as the flat part of a leaf rolled up in a funnel, the knots slide over the leaf as they are formed and suffer it to escape. When a tendril of Tamus has begun to curl near its extremity and to fasten itself round any object, if the upper portion of the same tendril chance to meet with another exciting body, another part of the same branch for instance, it may curl over again in a spiral at this point and tie its knots there. The same thing may happen a third time; and in this way may be seen in the same tendril two or three portions closely wound round an object, while the remaining part of the tendril is loose and detached. The contraction of the tendrils of the Tamus always takes place in the same direction, and the curling is turned inwards, whether there be or be not an object round which it may occur: and more than this, when a round