fibrils of nerves on which ganglia are formed belong to impeded sensation or impeded (involuntary) motion; for, in the ganglia, many nervous fibrils are seen running over the whole length of the ganglion, and forming no involvement with it. This circumstance of there being two kinds of ganglia will be found to obviate many difficulties which have hitherto attended the physiology of these bodies.

The leading heads, then, of this new system of the intellectual functions are as follows:

1. That the nerves of sensation arise in the organs of sense, and, by means of the anterior fibrils, terminate in the anterior columns of the spinal marrow.

2. That those nerves of sensation which do not terminate in these columns, pass directly to the cerebrum.

3. That the anterior columns of the spinal marrow terminate also in the anterior part of the cerebrum.

4. That these nerves and columns are the sensitive or ascending nerves and columns.

5. That it is in this way that sensation becomes perception, and that are excited in the cerebrum the faculties analysed by Gall and Spurzheim.

6. That the cerebral influence passes to the cerebellum by means of the corpora striata posteriora or thalami, the anterior peduncles of the cerebellum, &c.

7. That the cerebellum is the organ which gives impulse to all muscular motion, voluntary and involuntary.

8. That the posterior columns of the spinal marrow originate in the cerebellum.

9. That from the cerebellum arise also several nerves of volition. 10. That those nerves of volition which do not arise directly from the cerebellum, spring from the posterior columns of the spinal marrow by means of the posterior fibrils.

11. That these nerves and columns are the motive or descending nerves and columns.

12. That as there are two great encephalic organs, two anterior and two posterior columns of the spinal marrow, and two series of nerves, so there are two series of ganglia-ganglia on the sensitive and ganglia on the motive nerves.

13. That the intensity of the intellectual functions is as the length of their organs, and the permanence of these functions as the breadth of their organs.

I believe that not one of these statements were ever made by any one before they were made either here or elsewhere by myself; but should any of them have been previously made on any rational ground, I shall feel no pain in resigning the merit or demerit of their discovery to its proper author. Still less, of course, has the general system which I now advance been thought of by any one. It appears, then, that there is a species of circulation in the nervous system, of which I have sketched the general course, as curious and admirable as that which exists in the vascular (the

centre of the one being the heart, and of the other the head); and that there is scarcely any point of the body which this circle does not involve and rest on, since from almost every point ascends impression to the cerebrum by a nerve of sensation, the anterior nervous roots, and the anterior columns of the spinal marrow; and to each returns expression from the cerebellum by the posterior columns, the posterior nervous roots, and the nerves of volition. Nothing perhaps more than this beautiful correspondence between the vital and intellectual systems is calculated to raise the mind to him of whom the wisdom is testified by all that lives, from the most simple to the most complex of beings-from the polyp which can boast no other organ than a stomach, to man who has an intellectual system thus wonderfully complex and beautifully symmetrical.

Having, Sir, been long engaged in dissections of the brain of fishes, amphibia, and birds, in order further to illustrate and establish these important truths, I shall, on their conclusion, be happy to communicate them through the medium of your Journal. But you will excuse my in future not replying to statements so hastily made as those in answering which I have been reluctantly compelled to occupy so much of your present number-statements in which a confident reference is made to a book for a doctrine which that book, on the contrary, most pointedly contradicts; and to the animal body for a structure which has no other foundation than in the writer's mistaking the branches of a nerve for its roots.

I am, Sir, with great respect,

Your most obedient servant,

ALEXANDER WALKER,

ARTICLE VII.

A Memoir on Iodine. By M. Gay-Lussac.

(Continued from vol. v. p. 413.)

Observations on Chlorine.

THE analogy which I have established between chlorine, sulphur, and iodine may serve to throw some light on some of the combinations of chlorine, as I shall endeavour here to show.

M. Thenard and myself were the first persons who showed by a numerous series of experiments, that oxymuriatic acid might be considered as a simple substance, as there was no direct means of showing the presence of oxygen in it. We had even given this hypothesis at full length, in a memoir which we read to the Society of Arcueil, on the 26th of February, 1809; but it appeared so extraordinary, that M. Berthollet prevailed upon us to state it with the greatest reserve. In fact, though Davy has announced in his memoir on oxymuriatic acid, that this hypothesis had been advanced by Scheele, it was entirely new, and it appeared extra

ordinary only because it was in opposition to a manner of thinking fortified by long habit and by many good experiments. It was making a great step towards the knowledge of the real nature of oxymuriatic acid, to have questioned the received opinions respecting the nature of this acid: for it is much easier to find a new truth than to detect an old error. And we claim it as our own property, that we first perceived that oxymuriatic acid might be considered as a simple body. Davy, in adopting the conclusion which we had drawn from our experiments, has added nothing to its certainty; but we must admit that he has illustrated it at great length, and by the influence of his great abilities, has contributed very much to propagate it. I ought to observe, however, that M. Dulong and M. Ampere had adopted it long before Davy, and that I myself had always stated it as the most probable opinion, in the courses of chemistry which I delivered at the Polytechnic School. At present the discovery of iodine appears to have fixed the opinion of the French chemists on the nature of oxymuriatic acid. I shall therefore refrain from all discussion on the subject.

Admitting then that oxymuriatic acid is a simple body, it becomes in the first place necessary to introduce a modification into the proportions of the muriates. But as this does not follow immediately, from oxymuriatic acid being a simple substance, it may be necessary to justify it. Admitting a muriate to be a combination of muriatic acid and an oxide, it is possible that the hydrogen of the acid and the oxygen of the oxide may not form water; but may remain in the salt. I exposed in succession barytes, strontian, lime, and oxide of zinc, to the action of dry hydrochloric gas, in a glass tube, to a temperature approaching to a red heat, and I always obtained a great deal of water. To verify the same fact on potash, I put about a gramme of potassium in a platinum crucible, melted it, and plunged it into a glass vessel filled with hydrochloric gas. When the combination appeared complete, I weighed the crucible exactly, and then poured water on the salt, which occasioned no effervescence. The salt beeng dried in a low temperature, was found not to have increased in weight, nor after being fused was it found to have lost any thing. We ought then to admit it as a certain fact, that the muriates are all changed into chlorurets when melted, or even dried, and some of them even by being crystallized. We may suppose, as we have done for the iodurets, that the chlorurets dissolve in water without undergoing decomposition, and that when we unite hydrochloric acid with an oxide, the hydrogen of the acid and the oxygen of the oxide form water.* Whether this be the case or not, nothing but chlorurets exist at a red heat. It is therefore of these compounds that it is necessary to determine the proportions.

I have found (Mem. d'Arcueil, ii. 168) that 100 parts of silver take 7.6 of oxygen. Berzelius instead of that number gives 7.44. Though it be difficult to say which is most exact, I shall adopt this

See Note A.

last number, and will adnit further with Berzelius, taking the mean of his results that 100 parts of muriatic acid free from water combine with 424.92 oxide of silver. * Now these 424.92 of oxide are composed of 395.50 of silver, and 29:42 of oxygen. And since in the muriate the silver is in the metallic state, we must, in order to have the weight of the chlorine, add that of the oxygen to the weight of acid which we supposed to be combined with the oxide. We shall thus obtain for the composition of chloruret of silver

Thus, having the proportions of the muriates, we must, in order to obtain those of the chlorurets, add to the quantity of muriatic acid that of the oxygen supposed to be combined with the base.

According to the preceding ratio, and the composition of muriate of potash, as found by Berzelius, namely:

I have adopted this last proportion, which differs but little from that obtained directly by M. Thenard and myself.

We find likewise from the same data, that the ratio of oxygen to chlorine is that of 10 to 43·99, or in round numbers 10 to 44. It is therefore nearly three times as great as that of oxygen to iodine. If from the ratio of oxygen to iodine and chlorine we seek the density of chlorine, on the supposition that that of iodine is 8.6095, as we found it above; we find that it is 2:427, instead of 2421, which was deduced from the supposition that the specific gravity of hydrochloric gas is 1.247.

The great analogy which I found between iodine and chlorine ought naturally to lead me to believe that the salts known by the name of hyper-oxymuriates, are analogous to the iodates; that is to say, that they are combinations of the alkali, with an acid composed of oxygen and chlorine.

It is easy to see that on this hypothesis the acid cannot be the gas found by Davy, and called by him euchlorine. Chemists are nearly agreed that 100 parts of hyper-oxymuriate of potash, when

* I found 418.2. Mem. d' Arcueil, ii. 168.

decomposed by heat, give out about 38.88 of oxygen, and that there remain 61.12 of what has been considered as neutral muriate of potash; but which is, in fact, chloruret of potassium. From the proportions. given above, the 61.12 contain 28.924 chlorine, and 32-196 potassium. Now this quantity of potassium would take 6.576 of oxygen to convert it into potash. There remain, of consequence, 38.88 6.576 32.304 for the 28.924 of chlorine; hence the acid which I suppose to exist in hyper-oxymuriate of potash must be composed of

Chlorine

Oxygen

100

111.68

and the oxygen will be to the chlorine in a proportion five times greater than that which I have already given. It deserves attention that the proportion in weight of the potassium in the chloruret, ioduret, and sulphuret, is nearly the same as that of the oxygen in the chloric, iodic, and sulphuric acids.

According to Davy euchlorine gas contains one volume of chlorine and half a volume of oxygen; and taking 2:421 for the specific gravity of chlorine, we find that euchlorine is composed by weight of

This last number, multiplied by 5, gives 113.95, and though it differs from 111.68, we may, notwithstanding, conclude, that the acid existing in the hyper-oxymuriates, which I shall henceforth call chloric acid, contains five times as much oxygen as euchlorine gas.

If we dissolve chloruret of potassium (composed of 100 chlorine and 111.31 potassium) in water, and suppose that the water is decomposed, we will have hydro-chlorate of potash, admitting the oxygen to combine with the potassium and the hydrogen with the chlorine. But if we suppose the oxygen to unite with the chlorine, we form exactly euchlorine gas. I consider this gas formed by the combination of two parts in volume of chlorine and one of oxygen, as analogous to the protoxide of azote, which contains two volumes of azote and one of oxygen. Hence I propose to distinguish it by the name of oxide of chlorine. We may likewise distinguish by the names of oxide of sulphur and oxide of iodine, combinations of sulphur and iodine with oxygen, in the same proportions in volume. The first gives by weight about 10 oxygen and 20 sulphur; the second 10 oxygen and 156-21 iodine. I think it very probable that chlorous and iodous acids exist analogous to the sulphurous and nitrous, which ought to be composed of one volume of chlorine or vapour of iodine, and 15 of oxygen.

It appears to me demonstrated from the quantity of oxygen in oxide of chlorine, that this oxide does not exist in the hyperoxymuriates. Davy, however, is of a different opinion, for he