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 cere. bral 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. N° I.

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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 energy 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 (I 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 experiences 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.

These

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. tracheæ 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 distinguished 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 trachea 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. is easy, by opening them, to perceive the common trunk of the arterial trachea, 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.

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In the phalangium and analogous genera, only a single order of tracheæ 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 tracheæ. 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 larvæ 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 tracheæ, we see them always formed by a common trunk, which opens into the stigmata, and from which numerous ramifications procced, which are distributed to all parts of the body. This common trunk extends from one extremity of the body to another,

* See Traité Anatomique 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 trachea 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. 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 tracheæ. 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 trachea 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 trachea 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 tracheæ 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. general the abdominal trachea are of a silver-white; those of the

In

corcelet have a shade of red. The stigmata of this species placed upon the inferior sides of the abdomen are rounded and bordered by a salliant fold of the coreaceous envelope.

Several of the orthopteres exhibit at once arterial and pulmonary tracheæ. Of this number are the forficulæ, blattæ, phasmes, mantes, achetes, locustæ, mole crickets. But as these trachea are not similar in different genera, and as their complication is not quite the same, we shall make them known in those in which it presents the greatest peculiarity.

The respiratory organs of the forficulæ and blattæ present little difference. They are composed of a system of arterial trachea formed by a common trunk, which extends from one extremity of the body to another, and into which transversal trachea pass, which are distributed in a great number of parts. In the head they furnish the ramifications to the principal muscles, especially to the adductors and abductors of the mandibles and oesophagus. They then extend in the corcelet by two principal trunks which lie below the pulmonary tracheæ, but which soon divide, giving out numerous ramifications to the muscles of the corcelet, to the intestinal tube and the first pair of legs. The principal trunks continue to the thorax, keeping on the sides of the body. They then send a pretty large branch, which passes into the opening of the tremaer, to take up the air which other ramifications distribute in the muscles contained in the thorax, and in those of the wings and legs. It appeared to me that the arterial tracheæ furnished in the corcelet and thorax branches which spread in the legs, where they give out a much greater number of ramifications than the pulmonary tracheæ, which equally make their way thither. The trunks of the arterial tracheæ communicate with those of the pulmonary trachea by lateral branches proceeding from the internal sides of these trachea. The same thing takes places in the corcelet, the thorax, and abdomen. The same tracheæ form round the stomach and its appendages nets of tracheæ quite inextricable.

The arterial tracheie, after having given numerous ramifications in the thorax, extend themselves in the abdomen by a common trunk, which opens into the six stigmata placed on the sides of the body. It is likewise near these stigmata that the common trunks furnish each two bundles of transversal tracheæ; so that there are 24 such bundles in the abdomen. These same tracheæ make all the parts enjoy the impression of the air, distributing themselves over the intestinal viscera, the organs of generation, and the abdominal muscles. I must observe that the communication of the arterial and dorsal trachea takes place by means of transversal branches, which the first send off at intervals to the second.

The pulmonary tracheæ appear equally in the head, where they extend round the superior portion of the cerebriform ganglion and round the eyes, whether single or compound. They give out but a small number of ramifications in the head; and passing through the superior portion of the occipital foramen, they go to the corcelet,