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a description of the maculated or ship fever, which prevailed at the South Boston and Deer Island Hospitals.

Dr. Upham had been convinced of the distinct nature of typhus and typhoid fever by his own observations in 1847-48, and he seems inclined to subscribe entirely to the views of Dr. W. Jenner, as to the existence of four distinct diseases, long confounded under the head of " continued fever.” Dr. Upham arrives at the conclusion, that the typhus of Great Britain and Ireland is the same with that which raged on the shores of America in 1847–48; the disease in both instances presenting a like adynamic character, and requiring a similar plan of treatment. His observations will, of course, be read with greater interest in America than here, on account of the comparative novelty of the disease in that country.

Dr. Arnold's essay on the relation of bilious and yellow fever is a practical contribution to a subject on which, notwithstanding the great accumulation of facts, the state of opinion is still unsettled. The highest anthorities, however, and those whose opportunities of personal observation have been greatest, seem to be fast ranging themselves on that side of the question which regards yellow fever as a peculiar pestilential disease, by no means to be confounded with the common bilious remittent of warm climates. Dr. Arnold is a supporter of this opinion, and his remarks are valuable, as being those of a practical man who has had extensive opportunities of comparing the two diseases, and who has been led, by the observation of facts, to a view of the subject different from that which he originally entertained. The observations of Dr. Arnold are directed to two principal points of inquiry :--First, is yellow fever a distinct disease, or only a more malignant form of bilious remittent! Secondly, Is yellow fever contagious or not? On the first of these questions, he holds that yellow fever is, without doubt, a disease sui generis ; and he founds this belief as well on the symptoms during life as on the appearances after death. We regret that we have not room to particularize points of contrast between the symptoms of yellow fever and of bilious remittent. Among the necroscopic appearances, à pale anæmic condition of the liver is considered by Dr. Arnold as the most peculiar and invariable. The second question-as to whether yellow fever be contagious—is answered by Dr. Arnold decidedly in the negative. " addendum,” Dr. Arnold gives the details of three cases, which

prove

" that sporadic cases of yellow fever do occur, having all the symptoms of those during an epidemic, and the same pathological appearances after death."

We have read Dr. Arnold's pamphlet with pleasure; it is the production of a man who takes a sincere interest in his subject, and who records, without fear or prejudice, the results of personal observation.

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Art. XIII.— Summary of New Publications.

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Among the numerous works which the past quarter has brought, there is one which in regard to intrinsic value and physical size claims the first position in this summary. It is the Cyclopædia of Anatomy and Physiology,' edited by Dr. Todd, which was commenced in 1835, and has now reached its termination. There are few of our readers who have not profited by the instruction which this great work conveys, and who will not be ready with us to congratulate the editor upon the successful conclusion of his labours. We hope in our next to devote a full consideration to the aspects of physiology as presented by the Cyclopædia. The subject that has specially engaged medical attention during the past months, Diphtheria, forms the subject of numerous contributions, which we also intend to analyse in our October issue ; one of the volumes of the new Sydenbam Society consists of the Memoirs of Bretonneau and other French authors on this subject, edited by Dr. Semple ; Drs. Copeman and Ranking, and Mr. Ernest Hart also present us with papers on Diphtheria as observed in different parts of England. The first part of a work by Dr. Hirsch on the Geographical Distribution of Disease, promises to become an important contribution to medical literature. The influence of the Variation of Electric Tension on Epidemic and other Disease,' is considered by Mr. Craig, and will receive further notice. Dr. Headland's valuable essay on the Action of

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Medicines on the System bas already reached its third edition. A work entitled “Art versus Nature in Disease,' by Mr. Ilenriques, is devoted to an elaborate attack upon

the work of Sir John Forbes- Nature and Art in Disease '—upon the ground of the latter being, “however cunningly devised and carefully concealed, an attack upon the assumed delusion of the homeopathic system of medication." In a pamphlet of fifty-six pages Dr. Roods discusses Sciatica and Spinal Irritation ; from Dr. Handfield Jones we receive a further exposé of his views regarding the influence of the malarious poison in producing many prevalent disorders that are commonly classe d among neuroses, under the title of • A Tract on Neurolytic and Aguish Disorders, which we recommend to the careful attention of our reailers. From Vienna the Report of the great Hospital of that town for 1858, drawn up by Professor Haller; and from Philadelphia the essays of Dr. John Kearsley Mitchell on various medical subjects, have reached us.

Among the surgical works before us we would first mention Mr. Tomes's “System of Dental Surgery,' a work that will doubtless create an era in that department, and which we hope to analyse in our next number; the subject of Hæmorrhoils and Prolapsus of the Rectum finds an exponent in Mr. Henry Smith; Mr. Butcher favours us with a third series of his . Reports on Operative Surgery ;' the January number of the Ophthalmic Hospital Reports,' with articles by Dr. Taylor, Mr. Hulke, Mr. Dixon, is before us. Dr. Fraser presents is with Crimean reminiscences in the form of “A Treatise upon Penetrating Wounds of the Chest;' a third edition of Mr. Chapman's work 'On the Treatment of Ulcers of the Leg,' a reprint of Dr. Coghill's Observations on Strabismus;' and a German work • On Stricture of the Urethra,' also deserve mention.

Obstetrical science brings us a republication, under the auspices of the New Sydenham Society, of Dr. Gooch's work «On some of the most Important Diseases peculiar to Women,' with other papers. It appeared thirty years ago, when British medicine was peculiarly barren of all sound information on the points to which it is devoted ; the value of its republication is enhanced by an analytical and arguinentative memoir by Dr. Ferguson, which is prefixed to the volume. With this volume we would also mention another publication of the same Society, which nothing but want of space

has prevented our already alluding to more fully, the translation by Dr. Whitley of Diday's * Treatise on Syphilis in New-born Children and Infants at the Breast.' "The Use of Chloroform and other Anästhetics, their History and Use during Childbirth,' by Dr. Chapman; and a reprint of Dr. Duncan's papers ‘On the Cervix Uteri in Pregnancy,' conclude our list in this department of medical science.

In psychology and mental pathology we have first to introduce Mr. Bain's new work entitled “The Emotions and the Will.' Those who are familiar with the “ Asylum Journal' will be glad to hear that the interesting papers of the learned cditor on the Psychology of Shakespeare have been republished in a separate form, with additions. The Scotch Commissioners in Lunacy have issued their first Report; from the English Commissioners in Lunacy we have received a Supplement to their Twelíth Report; we have before us a German work on General Mental Pathology, by Dr. Wachsmuth, with sundry Reports on Lunatic Asylums and continuations of the periodical literature devoted to Insanity.

Under the head of State Medicine and Sanitary Science, Dr. Milroy's paper on Quarantine claims to be mentioned; an article by Mr. Sidney Herbert, reprinted from the “Westminster Review,' On the Sanitary Condition of the Army ;' the second edition of Mr. Erasmus Wilson's translation of Hufeland's Art of Prolonging Life,' and the sixth edition of Mr. Wilson's Healthy Skin; a Popular Treatise on the Skin and Hair,' also come under the same category. We cannot conclude this summary without adverting to a charming little book by Mr. Grindon, entitled "Manchester Walks and Wild Flowers,' in which the young Manchester naturalist receives copious information available in his promenades in the vicinity of the El Dorado of cotton-spinners. We must also mention an inquiry by Dr. Struthers into the mode of Improving the Teaching in the Scottish Universities, in which the author advocates the licensing of extra academical teachers, so as to maintain a spirit of emulation in the professors; por may we omit a passing allusion to Mr. de Morgan's paper “On the Structure and Functions of the Hairs of the Crustacea.'

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PART THIRD.

Original Communications.

ART. I.

Entoptics. By James Jago, A. B. Cantab., M. D. Oxon, Physician to the Royal

Cornwall Infirmary.

(Concluded from our last.)

§ V. The Retina.

27. We do not find any spectres from the homogeneous hyaloid membrane (except possibly in a moving pencil minute dark dots from nuclei in it), but the rays of light in traversing the transparent retinal substance, encounter a set of bloodvessels, which, like much of the web in the vitreous, is visible with the naked eye against the sky, as dark shadows with lucid borders caused by light reflected from them, and therefore much brighter in the case of the whiter pulsating arteries than in that of the veins.

Nevertheless, though up to this time we have advantageously, as one means, practised our observations upon the shadows whilst they remain ocularly steady, the results to be earned by such method in the example before us are so obscure, that with that alone our investigations would be abortive; for it seems fruitless to search for a pair of shadows of any vessel in a couple of divergent pencils.

We are in condition to proceed, however, for by 10 we have an artifice which elicits these shadows with singular precision. When divergent rays impinge upon the retina from some point in advance of it, and we impress this point with a lateral motion with respect to the retinal surface illuminated by it, the shadows of all the vessels, which are at right angles to the direction traversed by the point, become conspicuous; and may, by great excursions of the point, be plainly detected making small excursions of their own in the direction in which the point moves, similarly to the conduct of the objects next them in the vitreous humour, but to a less extent; intimating by the deviation that the vessels figure themselves by true shadows, which are received upon a screen at a certain distance from their own site. Indeed, whilst the said movenent is inoperative for bringing such portions of the vessels as are parallel to it into view, the slightest degree of it suffices for those at right angles. But no sooner is the movement stopped than the apparitions summoned forth becoine latent again. Wherefore, if the point be made to describe a circle in a plane perpendicular to the optic axis, so much of the vasa centralia as occupy the illuminated portion of the retina will be completely disclosed, as. in their turn all will be crossed as required.

The very existence of the limited reflective margin proclaims that the vessels lie near the sentient points. From the same proximity there is no brightness from inflection within the bounds of the shadow, and no inflective fringes at the sides,—at least, none clearly pronounced, for I fancy that in using fine pencils in these movements I really discern a single subtile dark ring of this kind, round certain capillary dots.

Now, as a parallax attends the apparition in its maintenance by perpetual movement, the essential condition of the phenomenon must lie in the nature of the sense of sight,, and depend upon the fact of the shadow being ever thrown upon fresh sentient points,, as if when we would fain keep the shadow upon the same sentients, it oscillates somewhat over them so as to slur it and its bright borders into one another, or rather, as if the sentients refuse to reply nicely for more than an instant to a given stimulus. Thus, if we suddenly open an eye, that has been awhile shut, against the sky, or walk along by a hedge-row through which the sun shines, we get glimpses of the vessels.

28. Purkinje, to whom we owe these expedients for conjuring into view the vascular phantom, has bequeathed to us another striking one, the same in principle, thongh demanding a special explanation. This is that of waving a lighted candle before the face.*

Let us suppose (Fig. 5) A B A' to be a (circular) section of the sentient surface of the

FIG. 5.

B

F

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retina by the plane of the paper, in which the optic axis falls, and c to be the lenticular centre of the eye. Let A B and A' B' be equal chords of the circle cutting each other in E. Draw c d perpendicular to a B, and join by straight lines c with A, A', B, B', and E, producing c E to meet the circumference A' BA in F.

C D
Then EF=CF-C E.
But c E=--

And CD=C B COS B C D, whilst B C D=;

COS ECD A CB =(ACF+B C F)=1 (A CA+B C B'). Again, E CD=BCD --BCF=I (A CA' — в св'). Moreover c B, very nearly=C F. Hence, if A C A'=a, B C B'=B, E F=d, and the optical radius=r, the equation first given becomes

cos 4 (a +B)
+

(3)

cos 1 (a +B) Acquiescing implicitly for the present in the hypothesis that the vessels are in front of the sentient surface, if a be the retinal place at a given instant of the image of a candle-flame, which is being waved laterally before the eye to keep the vessels in sight, and E the place of some vessel; then b, found by joining A E by a straight line, and producing it to meet the surface, marks the point by which e will be seen. Then, should we

carry
the candle round to the opposite side of the eye,

that the shadow of E, whose position is supposed unknown, deviates equally, twice, in one plane, that in which the optical centre of the eye and the two resting points of the flame lie, then B' will mark the sentient place of the second shadow. Then, if we observe the whole angle a between the two resting points of the flame, and the angle, ß, between the pair

d=r{

SO

* Beiträge zur Kenntniss des Sehens, 1819, s. 89. Neue Beiträge, 1825, s. 115, 117. But it was Gudden (J. Müller's Archiv fur Anat. und Physiol., 1849, s. 522) who first noticed the parallax. However, he lett for Müller (Verhandl. der Med.-physik. Ges zu Würzburg, 1855, ss. 411-47) to propound the theory of the relation of the vessels to the “perceiving membrane” adopted in this paper. He arrives at conclusions precisely similar to the above by measurements and calculations from the properties of the chords of circles; yet as the relative determination of the primary sentient seat is of such a high physiological importance, I have ventured to deviate from his plan, of using the chords that cross each other at the vessel in two observations, as we draw them in the course of the rays that project the shadows from the image of the flame in the back of the eye to that of the vessel. Not only because by substituting equation (8) I obtain a simple way of calculating the direct removal of a vessel from the sentients, but because I thus get a formula convenient for instituting certain comparisons with other prima facie possibilities of structural arrangement, which I am induced to think deserve a closer consideration than H. Müller has bestowed upon such contingencies. It is not enough to show, in order to refute this notion, that with shadows reflected from behind upon an anterior sentient surface, there must be two images. There actually are supplementary shadows of the vessels ; one which seems to have escaped him altogether, which I shall describe in 81, and another which shall speak of in 32, as an undoubted shadow, which he regards as arising from pressure of the blood current in the central vessels upon the retinal sentients, a sort of picture I believe never to happen (36); or, at all events, regards as complicated with such a picture.

of shadows, we can determine the distance, D, of the vessel from the sentient surface. For example, let a=96°, B=4°, r= of an inch (8), then d=īdz of an inch, as is easily found by aid of a table of natural cosines. Thus in ordinary language, when we hold the flame below the eye, the capillary

, patch at the punctum aureum will appear above any objective point upon which we gaze directly, revolving round it with a notable parallax as the flame encompasses the optic axis, receding from the point should the flame approach the axis, and vice versâ ; the shadows of all the other vessels appearing in accordance with the plan of finding their places, as above expounded. So that it is indisputable that the shadowy figures of the vessels are projected by rays which diverge by reflection at the site of the image of the flame in the back of the eye.

With other conditions the same, the parallax is greater for a vessel more removed from the sentients. The principles of 4 and 10 apply here generally, the divergent pencil falling upon the vessels from very obliquely situated points, yielding much deviation of the shadow from its perpendicular retinal projection; the screen thus, too, becoming further separated from the object as the radiating image of the flame approaches it. So, as the candle travels about, do we see any two vessels which decussate one over the other, glide across each other from a consequent difference in parallax. Also the relations between the positions of the radiant points, the body and the screen (with an allowance for its obliquity), and the size of the shadow (3) hold good here also, whence the broad shadows afforded by a vessel when in the vicinity of the image of the flame. Were we, in figure 5, to join A and A' by a straight line, and draw a tangent at F, and produce A, B and A', B' to meet it, we should obtain a figure similar to so much of figure 1 as has reference to two divergent pencils (4), and we might use the equation given in connexion with it for finding the distance of E from the tangent, and thus at no great labour, as we know the size of the eye, to get d.

29. Yet, again, let a B (Fig. 6) and a' B be two equal chords of the outer of two concentric circles, in the plane of the paper, in which the geometrical and optic centres

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E F =

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of the eye are assumed to lie, and cutting the inner in E' and e respectively; c the eye's optical centre; and c d perpendicular 0 A' B. Draw the straight lines c A, C A', C F, CF' and c B. Then, as for fig. 5–

cos Z A C B 1

cos (1 A CB-BCF Or, using the same notation for the angles, and for E F, as for fig. 5, but calling C E, r, instead of c F, we have cos 1

()
d=(r+d)
; d

(4)
cos (4

( If E E' indicate a section of the sentient surface, and F B F' a section of some tunic without it, and light radiating from the image of the flame A, were to cause the point B in the tunic to be seen by being there reflected, e is the point by which we should behold it, and B C F the parallax. If the image of the flame rest at A', similarly, B C F' will be the parallax.

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