Oxima g such ined a h such to the se mai hall : ition ci atoms. analysis of Berzelius ; yet it is the weight of an integrant particle of oxalic acid, as any one may satisfy himself by examining the composition of the oxalatés, à table of which I subjoin for the satisfaction of the reader : Number of Weight of an integrant particle. Oxalate of potash ..... 1 oic + 1 p 10.634 Binoxalate of potash .. 2 Ox + 1 p 15.268 Quadroxalate of potash 4 0x + 1 p 24.536 Oxalate of soda ... 2 ox + Is 17.150 Super-oxalate of soda 3 ou + ls 21•784 Oxalate of ammonia iloš + 1 a 6.783 Binoxalate of ammonia : 2 ox + la 11.417 Oxalate of magnesia 1 x + 1 m 7.211 lime I oic + 8.254 Binoxalate of lime 2 ox + 11 12.888 Oxalate of barytes 1 x + 10 14.365 . strontian 10x + 1 st 11.534 alumina 1 6x + 1 al 6.770 yttria 1 oo t l y 13.034 glucina 1 ox + 1 gl 14:467 zirconia 1 x tl van 10.290 copper 2 ox + 10 19.268 potash-and-copper . 2 ox + 1 p +10. 29.902 soda-and-copper 30x + 1st lc. 32:410 ammonia - and 2 ox t l a tlc. 26.051 copper iron 2 ox + 1 i 18383 Peroxalate of iron 3 ox + 1 ¿ 23.017 Oxalate of nickel 2 ox + ln 18.573 cobalt 2 x + 1c 18.594 lead 2 ou + 1 l 37.242 zinc 1 x + 1 % 9.661 mercury 1 ox + 1 m 30.634 silver los + 1 s 19.348 bismuth. 10x + 17 14.628 manganese 2 ox + 1 m 17.101 A uranium 10x 1 u 19•634 o cerium 2 ox + 1c 23.115 platinum 1 ox + 1 p 17.795 All these salts corroborate the weight of an integrant particle of oxalic acid as deduced from the analysis of oxalate of lead. Here, then, we have two experiments of Berzelius, which are inconsistent with each other ; namely, the analysis of oxalic acid and the ; analysis of oxalate of lead. Both were made with the greatest care; but as they are inconsistent with each other, they cannot both be correct, and there can be no hesitation about which of them :} . . . this UN eni ought to be followed. The analysis of oxalate of lead, is much simpler, not liable to the same uncertainties, and susceptible of greater exactness than the analysis of oxalic acid. We ought, therefore, to be guided by it; especially as it is corroborated by various other very exact analyses, as those of oxalate of potash, Cher oxalate of ammonia, and oxalate of strontian. But if we adopt this determination, and compare it with the analysis of oxalic acid, Art we shall find that this acid must be composed of six atoms; pamely, three atoms oxygen, two carbon, and one hydrogen; and its composition will be Weight. 64•739 or 3 atoms = 3.000 1502 4.634 Now this is the composition of the acid which I deduced some time ago by comparing my own analysis of oxalic acid with the composition of oxalate of lead as determined by Berzelius. I, obtained for the composition of oxalic acid. Oxygen 64 Carbon 3% Hydrogen 4 100 My experiment was conducted with great care, and I still consider my result as nearer the truth than either that obtained by GayLussac and Thenard or by Berzelius. My excess of hydrogen amounts to about one per cent., and was probably owing to the salt which I employed in the analysis not being quite free from water. Mr. Dalton has adopted the same constitution of oxalic acid with the above, and probably he has been led to it by the same mode of reasoning from which I deduced it. I shall take another opportunity of examining the other acids analyzed by Berzelius, by applying to them the test of the atomic theory. What I have here said is sufficient to show us that the most cautious and elaborate experiments are not sufficient of themselves to make us acquainted with the composition of these intricatesh bodies; though such experiments afford us considerable assistance, and, when compared with the structure of the salts as explained by the atomic theory, will generally be sufficient to give us all the information respecting the constitution of these acids which we can foi expect to obtain, Observations on the Uses of the Dorsal Vessel, or on the Influence which the Heart exercises in the Organization of articulated Animals, and on the Changes which that Organization experiences when the Heart or the Organ of Circulation ceases to exist. By M. Marcel de Serres, (Continued from Vol. iv. p. 355.) I BEGAN the examination of the dorsal vessel with those species in which we see it beating externally. Among those I chose the larvae of the coleopteræ and lepidopteræ. The larva of the geotrupa nasicornis, being very common, seemed proper for my object. The dorsal vessel of this species is elongated and cylindrical. When separated from the muscles and fatty membranes which surround it, we see that its diameter is the same in almost the whole of its length, being only a little contracted at the two extremities. Having fully ascertained this disposition, I endeavoured to ascertain if there were any ramifications. For this purpose I examined it with the I greatest attention, and with the best glasses. The contractions were always confined to the dorsal vessel, and never extended beyond the canal which runs along the back. I then placed this vessel under the lens of my microscope, and could not perceive any ramifications, not even in the membranes which surround it. ' In vain I endeavoured to find some trace of them in the membrane of the intestinal tube, the fibres of the muscles, especially in those of the rings of the abdomen and mandibles, which ought to have presented them, if any had existed, in consequence of the energy of their contraction, and the need which these organs have of vessels. I then examined the dorsal vessel of the geotrupa nasicornis et punctata ; but all my attention was unable to discover the least ramification. I subjected to the same examination a very considerable number of coleopteræ, the largest that I could procure, as the ateuchus semi-punctatus, cetonia aurata et fustuosa, scarites gigas, cerambyx heros, blaps gigas, and mortisaga. In all of them í I observed the dorsal vessel without any ramifications. These disseca tions, however, convinced me that, without a certain attention, ramifications of that vessel may be supposed to exist, on account of the colour and disposition of the hepatic vessels, which, being long and almost capillary, spread over every part of the body, and are often found fixed to it after the intestinal tube has been removed. To determine with certainty this disposition, we must allow the intestinal tube to remain, and dissect in water. This liquid lifts up the hepatic vessels ; so that it becomes easy to follow them to their Though I could not perceive any ramifications in these species, I was not entitled to conclude that they did not exist in insects. I intricas wistance lained / all و insertion. tract ever do no NOOS specie pertec almare this sa therefore made new dissections. The locusta gygantea being the largest insect in Europe, I made it the subject of my new observa body tions; but I was not more fortunate in that species than I had been paren in the preceding. The same thing happened with the locusta brevipennis, verrucivora, grisea, gryllus lineola, and migratorius. duced Though all these species are of a considerable size, I tried new dissections on the blatta occidentalis, acheta campestris, empusa pau pende perata, and mantis religiosa. In all these I found the dorsal vessel without any ramification ; and what assured me of this was, that after removing it with the greatest care, I could perceive no trace of rupture, which would have been the case if it had been torn from the ramifications of that vessel. No liquid was ever seen to run out; but this, as we shall show hereafter, might depend upon a variety of circumstances. But it was necessary to verify the observations of Comparetti. For that purpose I examined the dorsal vessel in a great number of butterflies, tenebrios, and crickets. All these dissections confirmed the results that I had already obtained. The same was the case when I studied the organization of the sphinx, noctua, and telligonia, all of them insects of a large size. It remained to be seen whether the dorsal vessel of flies and of syrphus presented any ramifications, as Comparetti has described such with considerable detail. I saw in general in the dipteræ and hymenoptere the dorsal vessel exhibiting numerous contractions ; but I was never able to perceive either vessels or pulsations along the side of the dorsal. vessel, Yet I studied this vessel in the scolia flavifrons, apis violaced, and syrphus bifasciatus of Panzer, the largest species to be found in the south of France. I then took the apis mellifica, which Comparetti mentions expressly. Though the research in this case was more difficult, on account of the smallness of the species, I did not perceive the cylindrical vessels, of which that anatomist speaks, and which according to him proceed from the extremity of the dorsal vessel, one going to the upper part of the body, the other to the lower. Though the disposition here mentioned by Comparetti indicates the regular course of a vessel, I still believe he was deceived by the appearance of the hepatic vessels. I terminated these first researches by the examination of the larvæ of the lepidopteræ. I chiefly dissected those of the sphinx, of the tithymale, and of the bombyx of the mulberry. All these larvæ appeared to me to have a dorsal vessel without any kind of ramification. I sought likewise to discover some traces of vascular vessels in the cellular or muscular coats of the intestines-coats which certainly would have received them if any had existed, for it is well very The known that the digestive apparatus is very distinct in larvæ. The di muscles of the mandibles, examined with the same design, appeared equally destitute of all vestiges of vessels, with whatever care I examined them. These facts prove that the dorsal vessel in insects is a canal almost eylindrical, only a little tapering af its two extremities. Its con izve this tractions are so distinct as to be perceptible on the outside of the body when the skin is not thick, and has a certain degree of transparence. The contractions of this vessel are irregular, and scarcely ever isochronous. This irregularity shows that they are not produced by a liquid in circulation. We shall find hereafter that they do not depend upon that liquid, and that they appear even independent of the organization of the dorsal vessel. These contractions are not equally strong, nor equally numerous, in all the species. Though it is difficult to determine any thing precise on this head, yet they seem more distinct in the larvæ than in the perfect insect. This difference is least distinct in the voracicus larvæ, as those of the geotrupa nasicornis, and certain species of sphinx and bombyx. As to the liquid contained in the dorsal vessel, its colour has always a relation to that of the adipose substance which surrounds this same vessel ; consequently it is not uniform in the different species. We observe in fact that the fat, which surrounds the dorsal vessel, has always a colour analogous to that of the liquid contained in the dorsal vessel. This constant similarity of colour may lead to the suspicion that the dorsal vessel is destined for the secretion of that matter so necessary in animals, whose parts increase rapidly when they are transformed into new crgans different from those which existed before, The humour of the dorsal vessel, then, exhibits various shades of colour. It is deep brown in most caleopteræ, greenish in certain orthopteræ, yellow in the silk-worm, orange in the caterpillar of the willow, transparent in the larvæ of the great butterfly (paon), and of very light colour in most of the lepidopteræ. When examined before the microscope, this humour appears composed of a great number of globules, the transparency of which depends upon colour of the humour itself. This organization announces an analogy of this humour with fat. Like it, we see it composed of small grains, which before the microscope appear each to consist of other smaller grains. These grains are merely little globules of fat, which swim, or are contained in small spherical and membranous sacks. The fat is contained in membranous sacks; for of itself it is fluid, and runs out easily when the sacks are pierced with the point of a fine needle. When thus extracted, it renders water muddy, and divides into small masses. The humor of the dorsal vessel put into water easily mixes with that liquid. A drop of it spread upon a piece of porcelain hardens by evaporation, and then resembles gum. The coats of the dorsal vessel are in general very thin. It would be difficult to say to what class they belong: As far as I can judge, the external membrane is cellular, and the internal muscular. The dorsal vessel is kept in its position by numerous tracheæ, several of which lose themselves in it. It is probable that these tracheæ, by their crossing each other in every direction, form the outer coat of the vessel. What proves this is that, in certain species, as the larve of the bombyx pavonia major, we see the dorsal vessel as if Vol. V. N° III. N a the |