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1847] Cumming on the Luminosity of the Human Eye. 337

was always seen much more readily and brilliantly when the eye was turned slightly to the side, and the rays of light passed through the pupil obliquely. On passing to the other side of the door, the luminosity was seen with greater difficulty. In this position it is necessary to have the eye turned to the side, to exclude all rays by the hand except those passing directly to the eye. In this way the reflection may be seen distinctly at the distance of eight inches.

"In the majority of cases, however, it may be seen as follows: Let the person under examination sit or stand eight or ten feet from a gas-light, looking a little to the side; standing near the gas-light, we have only to approach as near as possible to the direct line between it and the eye to be viewed, at once to see the reflection. Or, in a dark room, a candle being placed four or five feet from the eye, if we approach the direct line between them we shall be able at once to see it in many cases. If solar light be admitted through a nearly-closed shutter into a dark room, the luminosity may be seen when the pupil is tolerably dilated, the patient standing five or six feet from the aperture, and the observer occupying the position before indicated.

"These then are the circumstances necessary for seeing the luminosity. a. That the eye must be at some distance from the source of light; the distance being greater in proportion to the intensity. b. That the rays of light diffused around the patient (and sometimes around the eye itself) should be excluded. c. That the observer should occupy a position as near as possible to the direct line between the source of light and the eye examined; hence it is sometimes necessary for the observer to stand obliquely, that his eye may approach nearer to the direct line.

"The appearance of the reflection itself not only varies much in colour and intensity in different persons, but also from the circumstances under which it is seen, viz. the greater or less intensity of light, the position of the eye examined, and the distance at which it is viewed.

"When the reflection is seen under the influence of a dim light, as that from a candle, or a few solar rays, a red lurid glare, like that from a dull coal fire, is observed, evidently proceeding from the bottom of the eye, and, though not distinctly concave, yet conveying the idea of concavity. The character of the reflection thus seen by a faint light, at the distance of two or three feet, is very uniform, and does not present much variety of tint.

"When the eye receives rays from a good bright light ten feet distant, and we stand near the light, the reflection is then seen extremely brilliant; presenting a fine metallic lustre, and varying from a bright silver or golden to a decided red tint the latter being the more usual colour. While viewing the reflection at this distance, it sometimes undergoes a distinct change, suddenly altering from a copper or red colour, to a silver tint: this happens sometimes in consequence of a slight movement of the eye, but not unfrequently is observed without any movement having taken place.

66

Although the reflection is more readily seen in an eye with a large pupil, its lustre does not depend upon this circumstance. In two eyes with pupils of equal diameter, the intensity of the reflection frequently varied greatly. In one case, in which the reflection was very dusky in appearance, and the pupil small, atropine was dropped into the eye. I then observed that, though the extent of luminosity was increased, it still retained the same dusky hue. The greater facility with which the reflection is seen when the eye is directed slightly away from the light, appears to depend on the more patulous condition of the pupil.

"On approaching within a few inches of the eye, the reflection is not visible, for, before our eye can be brought within range of the reflected rays, the incident rays of light are excluded. On placing before the eye examined, a black card with an aperture the size of the iris, the intensity of the reflection was observed to be somewhat diminished.

"In cases in which the lens had been removed, the reflection was indistinct

at a distance, but was rendered somewhat clearer by the aid of a double convex lens placed before the eye examined; but at two or three feet distant, the reflection was as obvious as in cases in which the lens was present.

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Among the cases I have examined, I have recorded indiscriminately the appearance of the luminosity in twenty persons with good and perfect vision, whose ages varied from a few months to sixty years. In sixteen cases the reflection was bright and very evident; in four, faint, and seen with difficulty; and in one it was not seen at all; in the last case, the pupils remained small in the shade. If these observations are confirmed by other observers, we may say that the reflection ought to be seen in every healthy eye with a good-sized pupil." P. 287.

Mr. Cumming next endeavours to shew the source or cause of the reflection, which he ascribes to the choroid with its pigment. But, while he regards this as the principal reflecting structure, he believes that its effect is increased by the light returned from the retina and concavity of the hyaloid body. The reflection from these structures would be considerably increased in brilliancy, from the concentrating influence of the concave shape of the retina, and the focal distance of the lens. Our author makes some interesting observations on cat's-eye-amaurosis, and is inclined to think that two different things have been confused under this name—that, in the majority of cases in which the normal luminosity of the eye was observed, the reflection exactly corresponding with that described in this paper; and that the others, in which red vessels and a margin to the reflecting surface were seen, were cases of deposit of lymph in the retina. He states

"If this be a correct analysis of these cases, the mystery that hangs about cat's-eye-amaurosis vanishes; the first class of cases were cases of amaurosis arising from cerebral and other causes, in which, the retina and choroid being perfect, the normal reflection from them was seen; the second division consists of cases of deposit of lymph or other substances in or about the retina. It is then at once evident that a mere luminosity of the eye will in no case be a sign of altered condition. It will be necessary first to become acquainted with the normal reflection-its modifications in different lights and positions, and at various periods of life, and in persons of a dark or fair skin; then by the detection of an altered condition of such reflection (and assisted in many cases by contrast with the opposite eye), or by its entire absence, we possess a means of diagnosis in retinal and choroidal disease." P. 293.

In confirmation of its value, as a means of detecting changes in the retina, Mr. Cumming relates four cases. The first was one of imperfect vision of the left eye. The probability was " that it was an affection of the retina; but there was no other sign on which to rely but the statement of the patient with regard to the appearance of scintillations. The pupils were equally black, and the appearance of the eye normal; by this mode of examination it was rendered clear that the left half of the retina had undergone considerable change, and probably its power of transmitting the influence of rays onwards to the cerebrum." The other three cases are equally interesting, as showing the utility of this mode of detecting alteration in the retina. The fourth was one of cerebral amaurosis in which the reflection was perfect.

This is a communication of considerable value and interest, and highly creditable to the author. In establishing the fact of the normal luminosity

1847]

Thomson on the Constituents of Food.

339

of the eye, Mr. Cumming has discovered a mode of discriminating diseases of the posterior part of the eye which must prove of great service in many cases of difficulty.

XIX. ACCOUNT OF A CASE IN WHICH AN ABSCESS IN THE NECK COMMUNICATED BY AN ULCERATED OPENING WITH THE ARCH OF THE AORTA, AND IN WHICH THE HÆMORRHAGE DID NOT PROVE FATAL IN LESS THAN FORTY-EIGHT HOURS. By George Busk, Surgeon of the Hospital Ship" Dreadnought."

The title of this paper is liable to mislead. The abscess should have been termed fistulous. The patient was a woman about thirty-five years of age. An abscess in the neck, originating apparently in an enlarged gland, burst about four months before her death, and had continued to discharge matter ever since. Mr. Busk remarks

"The case is chiefly interesting as affording an unequivocal instance of a communication being formed between the cavity of an abscess and a large arterial trunk, in consequence of an ulcerative process being set up from without, and going on to produce such a thinning of the arterial tunics, that they finally give way under the impetus of the blood. It is evident that, had this communication been set up at an earlier period, and before the bursting of the abscess, it would have been very difficult, if not impossible, at that stage, to have avoided mistaking the abscess for an aneurism: for when, towards the end, the orifice was closed, and the cavity of the abscess filled with blood, such a pulsation was caused, as very strongly to simulate that presented by an aneurismal tumour." P. 301.

The extension of ulceration from a fistulous abscess to a large arterial trunk, as in this case, is not so rare an event as Mr. Busk supposes. The communication, however, of chronic abscess with a large artery by ulceration so as to simulate aneurism is extremely rare, so rare, indeed, that we know of no unequivocal case on record.

XX. ON THE RELATION BETWEEN THE CONSTITUENTS OF THE FOOD and THE SYSTEMS OF ANIMALS. By R. D. Thomson, M.D.

The author, in the present paper, gives the results of experiments on the amount of wax and oil contained in the food of two cows, as compared with the quantity of both of these found in the milk and dung. The details have been already printed in other treatises; to which he refers in the one now before us.

As it is evident then, that the present essay is itself an epitome of other works, the business of analysing it becomes more difficult. The first table informs us of the fact that cows taking certain food or foods, grass being one of them, give out much less oil and wax in their butter and dung than has been supplied to them in their food. That, on the contrary, when fed on other substances, hay being always one of them, they give out more oil and wax in their butter and dung than they have received in their food. We have no explanation offered of the cause of this difference, but an inference drawn that the oil in the food alone is not

adequate to the production of the oily matter in the cow; an inference which seems deduced from the latter to the exclusion of the former result just mentioned.

In another experiment, the carbon, hydrogen, nitrogen, and oxygen contained in the solid parts of the food and dung of a stall-fed cow were separately ascertained, and the difference estimated as the consumption of the animal. From the quantity of nitrogen thus consumed is deduced the amount of nitrogenous or nutritive matter assimilated by the animal, the rest being considered as forming the calorifiant portion of the food absorbed, and it is found that the former is to the latter as 1.560 to 13.100, or as 1 to 8 very nearly. Milk, as stated by the author, contains one part of nutritive to two parts of calorifiant constituents. Now, these may probably be taken as the extreme limits of the proportions which should be borne by the quantities of these respective principles when mixed in the diet. The growth of the young animal, and the demands arising from exercise of the muscular system in all requiring an increase, a state of rest admitting a diminished proportion of nutritive material.

Tables follow exhibiting the per centage of albuminous matters in a number of articles of domestic use as they occur in commerce, and also the relation of nutritive to calorifiant matter in many important items of diet. These are interesting and valuable, but we cannot extract, and it would be unfair to curtail, them. Another table gives the result that grass affords the best products when given to milch cows, although the animals receive less nitrogen when fed upon it than in many other cases; and the paper concludes with the remark that, the preceding observations lead to an extensive field of experiment and deductions of a highly practical nature, and may assist in indicating the direction in which the physician should pursue his enquiries when studying the laws by which the animal system is to be retained in a state of health. In all this we concur, considering the whole essay as offering some useful suggestions rather than pointing out any principles which are deserving of full confidence.

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We do not much like the tone of this paper: there is the appearance of putting too much on the author's own experiments, and referring too little to any other sources of knowledge. Thus, the author, having tabulated the results of feeding two cows on different articles, writes thus, we may infer from these results, that grass affords the best products, because the nutritive and calorifiant constituents are combined in this form of food in the most advantageous relations." Now, if the circumstance to be explained were a well-established fact, some value might attach to the proffered explanation; but, as compared with the vast accumulated experience of dairymen and others, how inadequate is this petty experiment to show us what kind of food causes cows to yield most milk and butter. As the case stands, we have merely a conjectural explanation of an inference founded on insufficient observation. We say conjectural explanation, for the Table only shows that the products in milk and butter do not increase with the quantity of nitrogen in the food.

At page 337 we have the following extraordinary passages.

"From this Table, likewise, we infer that, as nature has provided milk for the support of the infant mammalia, the constitution of their food should always be formed on the same model. Hence we learn that milk, in some form or other, is

1847] Latham & Bouillaud on the Diseases of the Heart. 341

the true food of children, and that the use of arrow-root, or any of the members of the starchy class, where the relation of the nutritive to calorifiant matter is as 1 to 26 instead of being as 1 to 2, by an animal placed in the circumstances of a human infant, is opposed to the principles unfolded by the preceding Table."

Now, how can a Table, which shows only the proportions between nutritive and calorifiant matters in milk, and several other alimentary substances, furnish the inference that the constitution of infant food should always be formed on the same model? Reflection on what we observe in Nature may teach us this, but Dr. Thomson's Table never can, albeit a good Table and teaching us an important condition existing in this model. We opine, too, that the discovery that milk is the true food of children has a date somewhat anterior to that of the construction of the Table in question. The Table unfolds no principles, but shows that the starches differ in an important particular of their constitution from the matters contained in milk. It is certain, therefore, that the starches alone cannot form an analogous diet; it is probable that the use of them as substitutes is not advantageous. We give the author all credit for the skill and labour displayed in his chemical researches, but wish to remind him, in conclusion, that, for the promotion of knowledge, legitimate inferences are as much needed as trustworthy experiments.

We here close our notice of this volume of the Transactions, which, with a few exceptions, fully sustains the high reputation of the Society. Often as we have had occasion to express our approbation of these annual volumes, we have seldom performed the task with greater pleasure than in the present instance.

I. LECTURES ON SUBJECTS CONNECTED WITH CLINICAL MEDICINE, COMPRISING DISEASES OF THE HEART. By P. M. Latham, M.D. Physician Extraordinary to the Queen, and late Physician of St. Bartholomew's Hospital. Vol. II. pp. 419. London : Longman and Co., 1846.

[Second Notice.]

II. TRAITÉ DE NOSOGRAPHIE MEDICALE. Par J. Bouillaud, Professeur de Clinique Medicale à la Faculté de Medecine de Paris, &c. &c. 5 Tomes. 8vo. 1846. Bailliere.

[Second Notice.]

In closing our notice of Dr. Latham's Lectures in our last Number, we intimated our intention of resuming it, so that we might have an opportunity of comparing his sentiments on some of the more important points in the history of Cardiac Diseases with those professed by certain cotemporaneous writers of the French School. We have selected M. Bouillaud as the representative of Continental Medicine upon this occasion, as being an author of unquestionably no ordinary talent, and one who has devoted his especial attention to the class of disorders in question, and con

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