cut; and they are, therefore, in so far subject to similar laws with liquids contained in tubes.*

It is, then, from Cuvier's not distinguishing between the height and the breadth of the organs, and their corresponding intensity or permanence of function, that his comparison of man and the bull, and his scale in general, which Dr. Leach has quoted, is of diminished value, and quite inapplicable to the present question. This curious and important fact may be illustrated even from the classes of animals; for the laterally compressed and high cerebellum of birds corresponds admirably with the intensity of their voluntary powers, and the depressed and flat cerebellum of the turtle, frog, salamander-in short, of all the slow but long moving reptiles, equally corresponds with the permanence of their voluntary power.

In reply to Dr. Cross's last observations (in the 30th number of the Annals), I need say little indeed. The strongest argument which he adduces in refutation of the preceding doctrine, is the ironical application of the words "logical and sapient," and the direct one of the words "absurd and groundless." Now whether Dr. Cross's authority in matters of science is sufficient to render such words, when used by him, the very death-warrant of a new doctrine, I am perfectly ignorant; but, with me, even much higher authority than the Doctor's would not constitute proof. Dr. Cross adds, "that volition ranks among the faculties of the mind, whose organ is the cerebrum ;" and so far as authority in general and the authority of Dr. Cross in particular goes, this is another proof of the falseness of my doctrine. The Doctor, however, further adds," that affections of the cerebrum, while the cerebellum remains sound, produce palsy, which I humbly submit is just a loss of volition." At last, then, the Doctor does give us an argument; and as it is a solitary one, and follows so much of mere authoritative determination, it must no doubt be so triumphant that the "humble submission" which the Doctor forgot when adducing his authority, but so generously appends to his proof, must be intended only to enhance talent by modesty, and to heighten triumph by moderation. This is certainly very fine; and it involves only one little awkward circumstance, which is, that while the Doctor's proof consists of two propositions, it presents precisely as many errors!" Affections of the cerebrum," says he, " while the cerebellum remains sound, produce palsy;" and hence he means to conclude that palsy which he deems a loss of volition, and consequently volition itself is dependent on the cerebrum, and not on the cerebellum: indeed he actually says so in the preceding portion of the same sentence; thus placing the induction (logically no doubt) before the datum, and

*It is perhaps also for the same reason, that, in a galvanic battery, the intensity of its action seems to correspond with the number of the plates (for the igniting power is as the number), and the permanence of its action with the magnitude of the plates. Accordingly, M. de Luc observes that the number of the plates is analogous to the length of a pump for raising water; and the size of the plates is analogous to the magnitude of the bore of the pump.

reducing it to a mere assertion. The conclusion, however, is inaccurate; for even if palsy were just a loss of volition, it would be by no means wonderful if the functions of the cerebellum were deranged by an injury of the cerebrum, since two immediately contiguous and intimately connected organs must powerfully influence each other. Dr. Cross must be aware that even remote organs evidence this sympathy; and it may even to himself have happened, that a deranged state, for instance, of the Doctor's bowels may have caused an affection of his head; but surely the Doctor would not therefore conclude that the cause of the derangement was in his head. Just so it is, that no derangement of volition caused by injury of the cerebrum is any proof that the cerebrum is the seat of volition. So much for one half of the Doctor's proof. In the other, he humbly submits that palsy is just a loss of volition. I reply that palsy is no such thing; and as the Doctor is fond of logic, I shall give him my proof in a logical form.-We cannot be conscious of any mental act unless that act exist; but volition is a mental act of which the patient is conscious in palsy; therefore palsy is not just a loss of volition!

Having thus, I believe satisfactorily, replied to the Doctor's argument against me, I must notice the claim which he sets up for himself. He has discovered, he says, that "the cerebellum supplies the face with nervous energy; and of me he asserts" that there is not even the smallest hint, from the beginning to the end of his tract, that could at all lead in the smallest degree towards this discovery." Now as that and the succeeding tract show, in great latitude and detail, that all muscular parts are supplied with nerves from the cerebellum or the posterior columns of the spinal marrow, and more especially that all those encephalic nerves which supply muscles of the face have at least one origin directly from the cere bellum, it is difficult to conceive how any Gentleman could venture to make so anxiously tautologous and obviously untrue an assertion as the preceding. In these tracts, I have said, "Like these (the spinal nerves), all the encephalic nerves have two portions-a cerebral and a cerebellic, except the first, second," &c. p. 175; and "The transverse bands (these are the pons varolii, the narrower and flatter band of Spurzheim immediately below it, and the much broader and radiating but perfectly flat band below that, which was first pointed out by myself) seem uniformly to serve the purpose of conducting the cerebellic origins of the nerves; "-p. 179. With regard to that encephalic nerve in particular which is by way of preeminence named facial, I have demonstrated the remarkable course of its two portions, cerebral and cerebellic, overlooked by all other anatomists-p. 148; and I have done the same with regard to several other nerves. These I think are proofs sufficiently ample to show how far the face (though opposed, in the sense above explained, to the cerebellum, that is in so far as it contains the organs of sense, and not as it is furnished with muscles) is yet dependent on the cerebellum for the supply of its muscular parts. These proots VOL. VI. No I.

C

I adduced six years ago; and yet Dr. Cross tells me I have not said one word of the cerebellum receiving nervous energy from the face, but that he has now made the discovery! Though, however, the muscles of the face thus receive motive énergy from the cerebellum, not one of its sensitive nerves are derived from it; for even the auditory nerve, after crossing the corpora restiformia, ascends to the cerebrum. As, then, the face receives only motive and not sensitive energy from the cerebellum, and as I proved this six years ago, I cannot divine to what discovery it is that Dr. Cross on this subject pretends. Having thus done justice to myself by exposing this ( dare say unintentional) plagiarism, I leave it to some friend of Dr. Crawford's to do him similar justice with regard to Dr. Cross's charcoal hypothesis of respiration.

(To be continued.)

ARTICLE VII.

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 expe riences when the Heart or the Organ of Circulation ceases to exist. By M. Marcel de Serres.

(Concluded from Vol. V. p. 379.)

1. Respiration in the Air by means of Tubular Trachea.

Division 1.-Only Arterial Trachea.

PULMONARY trachea exist in the greater number of the caleopteres; but there are certain genera, as the cerambyx, blaps, and most of tenebrunides, in which they are not observed. These trachea take air immediately, forming round the stigmata very numerous bundles. But that a communication may be established among all the trachea, there exists a common trunk which extends from one stigma to another, and which opens in that part. It is from this common trunk that these numerous bundles proceed, of which we have spoken, and which distribute the air to all parts of the body. The direction of the trachea, then, is almost always transversal. As these vessels issue in bundles from a common trunk, they present in some measure the disposition of a horse's tail. In the genera of which we are speaking, the trachea are very numerous in the breast; to such a degree, indeed, that they almost cover the muscles of that part. We see them all presenting a transversal direction. As they are very near each other, they form on the muscles parallel streaks, so very close together that it is with difficulty that any interval at all can be seen between them. These

pectoral tracheæ proceed from the common trunk, which takes up air in the first stigma of the abdomen.

In general the arterial trachea are very much branched, and give out an infinite number of ramifications. This disposition is very striking in the genera of which we are speaking, and which are dis tinguished by the position of their stigmata. These stigmata are placed below the elytres, and on the sides of the body in the back. It may be owing to the difficulty which the air finds to introduce itself into these stigmata, especially when they are concealed below immoveable elytres, as in the blaps, that the arterial tracheæ are so disposed that all parts of the body speedily enjoy the influence of the air. These stigmata are formed in the common way by a jutting out horny border of considerable thickness. Their opening is oval, and their greatest diameter is in a transverse direction. It is easy, by opening them, to perceive the common trunk of the arterial tracheæ, which opens there. The disposition of the arterial trachea in the cebrio longicornis is almost the same as in that which we have just described.

In the phalangium and analogous genera, only a single order of trachea is observed. The respiratory system in these genera may be considered as formed of common trunks, which, situated in the neck, are the centre from which all the other ramifications proceed. These common trunks are found near the stigmata, to which they send a branch; and from this point proceed two bundles of trachea, which spread over all the body, especially the intestinal viscera. We see even that they surround each appendix of the intestinal tube, and their first membrane is in part formed of these trachea. The common trunks continue thus along the sides of the body, giving out different branches to the muscles of the legs, to the mouth, to the dorsal vessel, and to the organs of generation. This respiratory system is one of the simplest. Only two stigmata exist, placed on each side of the corcelet, on the same line as the fourth pair of legs. These stigmata are oval, the greatest diameter proceeding from below upwards. Internally we see that they have a border pretty strong. They are very large, compared to the size of the body.

The larvae of lepidopteres, or caterpillars, have likewise nothing but arterial trachea. Lyonnet, to whom the anatomy of insects is so much indebted, had already remarked this fact. However, I thought it worth verifying in the caterpillars of different butterflies, especially in those of the cabbage and of fennel; in the larvæ of the bombyx pavonia major, mori, and in that of the sphinx atropos. In all these I found only arterial trachea. When there are only arterial trachea, we see them always formed by a common trunk, which opens into the stigmata, and from which numerous ramifications proceed, which are distributed to all parts of the body. This common trunk extends from one extremity of the body to another,

4

* See Traité Apatomique de la Chenille du Saule, p. 101 and 237, tab. x. fig. 2.

and its diameter is at least a millimetre (0.03937 inch); sometimes it is even more considerable. It is from this common trunk that the bundles of transverse trachee always divided into pairs proceed; the ramifications of which are generally unequal. The number of these bundles of trachea is always twice that of the stigmata, as two always proceed from each stigma.

The insects which respire air immediately, and which have only arterial tracheæ, are those in which the respiratory system is simplest. The species in which this disposition exists require to enjoy the influence of air as speedily as possible. Hence it is distributed almost as soon as it is received.

The pulmonary trachea of the scarites gigas originate above the cerebriform ganglion by a transversal branch, from which proceed ramifications to the upper lip, the antennæ, and the eyes. This branch is prolonged in the head by two principal trunks, which extend in the corcelet, and then in the rest of the body. These trunks having reached the corcelet, form on each side of the dorsal vessel a kind of semicircle, giving out numerous ramifications to the dorsal vessel and the surrounding muscles. The pulmonary trunks, when they reach the breast, approach the dorsal vessel more and more, forming on each side erismes, semicircles, from the centre of which proceed the branches that form a communication between the pulmonary and arterial trachea. The common pulmonary trunks continue in the same manner in the abdomen, where they form afterwards rings in semicircles, from which proceed the principal branches, which form a communication between them and the arterial tracheæ. As to the branches that come from the internal side, they all go to the dorsal vessel and the muscles that surround it. In this place the pulmonary trunks never acquire a large diameter.

The trunks of the arterial tracheæ rise below the cerebrum by two principal branches, which distribute themselves over the mandibles, and the different parts of the mouth. These branches have a very considerable diameter, and a reddish colour. When they come to the corcelet, they unite, and form only one trunk. After this they send a large branch to the first pair of legs; while from their interior side they send branches to the trunks of the pulmonary tracheæ, and to the intestinal tube. The same thing takes place in the thorax. These tracheæ diminish somewhat in size in the abdomen, and keeping always at the side of the body, the external branches go to the stigmata, while the internal surround the intestinal tube and the organs of generation with a fine network of tracheæ. The common trunks form from ring to ring semicircles, always furnishing the branches of which we have spoken. We observe that from each semicircle formed by the arterial trachea there issue two long cylindrical trachea, which ramify to infinity on the intestinal tube and the organs of generation. There are few species in which these trachea are more distinct or extensive. In general the abdominal tracheæ are of a silver-white; those of the