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invented a sort of double canula, which al-lowed him to take out the one to clean itwhile the other remained in ; then, whenthe one was cleaned, he put it in again. Theinstrument has shoulders made to it-shoulders to prevent its being swallowed, orpressing on the sides so as to hurt. Now,of late this sort of thing has been done inthis hospital, and in one case Mr. Stanleyperformed it ; but he thought it was a farbetter mode of cleansing the tube, to haveit made wide and funnel-shaped. By beingmade large at one end and funnel-shaped,he could take a little lint and clean it out.

FOREIGN DEPARTMENT.

The following cases are detailed inGriife’s and Walther’s Journal, (Vol. IX.p. 1,) by Dr. Wedemeyer of Hanover :-

Mortification of the Limb of a nTezv Born Child.A woman was brought to bed a month be-

fore her time with twins. One of the chil-dren was quite putrid, and dead born ; theother; however, was alive, but there wasgangrene of one of its lower extremities,extending from the foot to the knee. Theancle-joint was exposed, and both tibia andfibula were projecting through. The childdied on the following day. On examination,the femoral artery, half way down the thigh,was found closed by a caseous kind of lymph.During pregnancy, the mother had experi-enced nothing, to which the death of theone, and the mortification of the other child,could be ascribed.

Fcetics in Fcetu.

A young healthy woman of this place(Hanover) was brought to bed without anyassistance of a six or seven months’ child,on which the following malformation was ob-served. On that part of the child where theorificium ani is usually situated, there was alarge membranous bag, which, together withits contents, had already proceeded to an

advanced state of putrefaction. It containedsomething very similar to a placeuta, whichwas connected by almost imperceptiblethreads to a dead fcetus of about four or fivemonths. The foetus was unfortunately verymuch changed, still several parts were dis-tinct, as the head, face, vertebrae, and sa-crum.

The membranous bag, which, to a certaindegree, occupied the place of an uterus, wasconnected to the posterior part of the sa-crum of the child. Similar cases are to befound in Meckel’s Anatomy, his Archives,and in the Phil. Trans., Vol. XLV. p. 385.

On the probability of a Canal in the Optic Nerveof’ the Human F4ztus.

In 1816 I accidentally observed, whilstexamining a foetus of about five or six monthsold, that on gentle pressure of the globe ofthe eye, the vitreous humour escaped fromthe divided extremity of the optic nerve.On a more careful examination of this andother foetuses, both with and without theaid of optical instruments, there appearedto me a black point in the centre of thedivided optic nerve, in which there was anannular opening. Through this point thevitreous humour could be readily squeezedout. I then examined the end of the nerveterminating in the globe, and also observedin several subjects a dark spot with an au.nular opening.

I entertained some distrust of the cor-rectness of my own observation, and com-municated it to the late Dr. Albers, of Bre-men, and through him to Dr. Treviranus.This last increased my suspicion, by statingthat the canal in the optic nerve must havebeen produced artificially by the pressure.At the same time, however, Sommering’sdiscovery of a canal in the olfactory nerveof the fmtus occurred to me ; a canal whichcommunicated with the ventricles of thebrain, and in the lower vertebrated animals

always remained. Lastly, I recollected thiswell-ascertained fact, that in the humanfcetus, as well as in the lower animals, thecorpora quadrigemina, from which the op-tic nerves at least in part arise, are hollow,and that their cavities communicate withthe third ventricles. But I have not yet

been able to verify the circumstance, andit therefore still remains in dubio.

PHYSIOLOGY.

On the application of the Barometer to the studyof the circulation of the Blood, and respira-tion in Vertebrated Animals. By Dr.BARRY.*(Read at the Philomatic Society, March,1827.)

* Annales des Sciences Naturelles, April1827.

IT is at present established beyond doubt,that during inspiration in mammalia, a

tendency to a vacuum exists around andwithin the heart, and the cardiac extremitiesof the great thoracic veins. The Com-missioners of the Institute, MM. Cuvier andDumeril in their report have admitted thisfact as proved, but observed that in reptilesand fishes inspiration is performed by a kindofdeglutition, and not by the expansion of athorax ; and that, consequently, in tbes6

animals, the influence of a thoracic vacuumon their centripetal fluids, is, at least,doubtful.

This truly philosophical objection has

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eompelled me to search for better means,in order to determine if there exists a cen-tral vacuum in reptiles and fishes; and, con-sequently, if any portion of the pressure ofthe medium in which they live, is employedto assist the progression of their centri-

petal fluids.In the experiments which I made to show

the effect in quadrupeds, of the expansionof the thorax on the motion of the blood inthe veins, I perceived that the introductionof air, or other fluids into the circulatorysystem, might modify in some degree thephysiological state of these animals, andthat on this account my experiments wouldbecome less conclusive.

Moreover, it was evident that the instru-ments which I used, could not be employedon frogs, serpents, or nshes, and these in-struments did not present any means ofrecognising the absolute diminution of theatmospheric pressure around the heart, bythe motions of inspiration, even in mam-malia ; but by employing the barometer asan instrument of measuring in these experi-ments, we might arrive at the knowledge ofthese data, and avoid, at the same time, theinconvenience already alluded to.

Every person knows, that in the tube ofTorricelli, the column of mercury is ex-

actly counterbalanced by the pressure ex-ercised against its base by the atmosphericcolumn. Also, when this equilibrium is

changed by the diminution of the atmo-

spheric pressure, the mercury descends inthe tube, and indicates exactly the quantityof this diminution.

It appeared then to me evident, that ifthe thoracic cavity of a living animal wereplaced in communication with the reser-voir of the barometer, the column of mer-cury would mark precisely the diminutionwhich the dilatation of the thorax deter-mines, in the pressure exercised by the at-mosphere on the parts which are containedthere, as well as the increase of the pres-sure produced on the same organs by thecontraction of this cavity.

1 then ordered a barometer to be made,the tube of which was curved to the twenty- Isixth of an inch, and to such an angle thatthe mercury, in order to ascend a millime-ter perpendicular above this point, was

forced to occupy nearly five millimeters ofthe oblique tube. Thus, the mercury inthis instrument moved with a velocity and asensibility five times greater than in ordi-nary instruments.

Dr. Barry then relates six experimentswhich he made with this tube on birds,fishes, and reptiles, and which were fol-lowed by the same results ; one will be suf-ficient to show our readers the mode em-

ployed.Experiment.—I introduced a small tube

of steel, which communicated with thebarometer, between the heart and sternum ofa frog, whose abdomen was filled with eggs.

Such is the sensibility of the barometerthat, although the animal did not respirewith energy, the mercury proceeded in thespace of half a millimeter, and during thewhole time that the tube remained in thissituation, the movements of the mercurycorresponded exactly to the respiratorymotions of the breast of the frog. I took

great pains to ascertain this accurately, foran assistant indicated with a loud voice themovements of the column of mercury,whilst I held the tube in its place, and ob-served the respiratory motions of the animal.Each time that the frog performs the act

of deglutition, the air is forced into its lungs:the larynx, pericardium, and heart, ap-proaches towards the mouth, whilst the

mercury invariably fell.Dr. Barry draws from his experiments

the following conclusions :-1st. That in allvertebrated animals there

exists a mechanism, by the operation ofwhich a part of the pressure of the mediumin which they live can be raised around theheart and cardiac extremities of the centri-petal tubes.

2nd. That this pressure can be diminish-ed, either by the expansion of the thoraciocavity around the heart, or by the contrac-tion and locomotion of the heart within thiscavity, or by these means united.

3rd. That the amount of the pressurethus left without opposition, is employed todraw the centripetal fluids towards the re-lative vacuum in the breast of these ani.mals, that is to say, from the surface to-wards the centre.

4th. That this pressure, acting on allsides and on all extremities of the compres-sible centripetal tubes, must force the mo-lecules of matter, which can pass into theircavities, either by the pores, or by someother openings in their parietes.

5th. That as the centripetal tubes arecompressible to a great degree, this pressuremust act on their contents with a much

greater force than if these tubes were in-compressible, because in this last case thepressure could only act on the extremity ofthe column of liquids, whilst, in the firstcase, this pressure acts on all the sides andon the whole height of the column at thesame time.

6th. That the barometer, with a reser-voir sufficiently large, and an exact commu-nication with the cavity which surroundsthe heart of a living animal, gives a very ex-act measure of the diminution of the pres-sure, either by the dilatation of the thora-cic cavities, or by the contraction and loco-motion of the heart in the interior of thesecavities, or by all these means united.