rather tends to affect the colour of the latter, and the apparent brilliancy of the image which we see, than to give us a definite perception of the form and colour of the objects from which it is reflected. The less strongly developed the superficial pigment is, the less absorption and dispersion will take place.

"In various diseased conditions, the layer of the hexagonal cells becomes destroyed or atrophied, and in this case we may see the choroidal vessels very well, with their interstices filled with dark pigment; but this may sometimes be observed in the case of persons with well-developed interstitial pigment and little development of pigment in the superficial layer; such cases, however, are rare. Again, both superficial and deepseated pigment may be destroyed by disease, and then we see the choroidal vessels against the white grouud of the sclerotic; but something similar may be seen in the eye of an albino, or a person of very fair complexion. Finally, the choroid may be atrophied in its whole thickness at particular parts, as in staphyloma posterius, and we then see nothing but the white sclerotic; but this may be simulated by white patches, the result of iuflammatory exudation, fatty deposits in the retina, &c.

"In all such cases, we must pay particular regard to the complexion of the patient, and the history of his case. The seat of the abnormal appearance may often be detected by observing whether the retinal vessels pass in front of or behind the white patches observed; and we may generally distinguish the results of atrophy, or destruction of pigment from those of original conformation, by the irregularity of the distribution of pigment in the former case, and from those due to exudations, &c., by their not being so sharply defined in general.

"Masses of dark pigmentary matter are sometimes observed on the fundus oculi. They may or may not be of pathological importance; and a sickle-shaped deposition of this kind is common at the margin of the papilla optica.

"The transparency of the retina may be impaired, and its reflecting power increased in consequence of inflammatory disease. The effect of this is to give a hazy indistinct appearance to the fundus oculi. The observer must be on his guard against confounding this with an indistinctness due to improper focal adjustment of his own eye, or to turbidity of the media, or with the faint greyish colour which the fundus presents occasionally in very dark subjects-a phenomenon which appears to me to be explicable upon principles referred to in Part I. When the retinal is separated from the choroid by serous exudation, some parts may appear bluish grey, or white, and others almost black, according as the light regularly reflected from their surfaces enters the eye of the observer

A good deal also dependa upon the colour of the subjacent fluid, and upon contrast with parts of the fundus which present the usual

appearance.

"The papilla has a red appearance in various diseases, owing to in. creased vascularity of its surface; but its colour varies considerably in the normal state, often resembling grey cerebral substance, and it is sometimes pinkish. Some parts of it appear to reflect more light than others a fact which is attributable to our being often able to see back to the lamina cribrosa. The more brilliant parts correspond to those in which fibrous tissue predominates, and the darker ones to the trans parent substance of the nerve-tubes along the axes of which we look.

"The papilla sometimes appears abnormally large and vascular, viz., in cases of staphyloma posterius at a certain stage where the sclerotic appears around the optic disk in consequence of atrophy of the choroid; and small retinal vessels, which cannot be distinguished on the orange ground in a normal eye, come into view. Eyes affected with this disease are more or less myopic; and the optic disk proper appears hardly so white as the surrounding sclerotic denuded of the choroid.

"The choroid hardly comes to the margin of the place of entrance of the optic nerve, even in a normal eye, and on this account the nerve substance may be much atrophied, according to Liebreich, without an apparent diminution in the diameter of the disk.

"The papilla optica, which does not really present the form of a globular elevation during life, sometimes appears as if it did so when it is observed by means of the ophthalmoscope. One cause of this has been pointed out by Liebreich, who has drawn attention to the fact that the distribuition of dark and light coloured parts resembles that in a representation of a sphere well executed on a plane surface. When the optic nerve is cupped or excavated, as in glaucoma, this appearance comes out more strikingly, especially when the indirect method of examination is employed, because we are then subject to another optical illusion depending upon the reversal of the image, and similar to that in consequence of which the inverted image of an intaglio produced by a biconvex lens, resembles a cameo; the shadow thrown by the margin of the cup or excavation appearing to be on the side opposite to that from which the light comes to it instead of on the same side. This illusion is, for obvious reasons, most striking when the image of the disk is near to one side or other of the observer's field of vision.

• Grafe's Archiv, Bd. i., Abt. ii.

See "A Fragment on Glaucoma," by Dr. Mackenzie, in No. xi. of the London Ophthalmic Hospital Reports.

"In cases where the optic nerve is deeply excavated, the bottom of the cup appears to be of a greenish colour, while its margin (corresponding to the part of the sclerotic immediately surrounding the nerve, and not covered by choroid) has a yellowish white colour, and a brilliant aspect at certain parts from its reflecting the light like the rim of a cup. The retinal vessels may be seen passing over this to reappear indistinctly at the bottom of the cup, and they may seem more or less dislocated as they do so, according to the position of the patient's eye with respect to the observer, and according to the position in which the biconvex lens is held, if one is made use of."*

"When we perceive opaque bodies situated in the media, by means of light coming from the fundus oculi, they will appear black, whatever their real colour may be; thus, opacities in the lens, though they may appear grey, or even white, under ordinary circumstances and contrasted with a black pupil, appear like black spots or streaks upon the illuminated fundus. We may, no doubt, see light reflected from the fundus oculi, and light reflected from opaque bodies in the media at the same time, and contrast will then determine in a great measure the appearance presented by the latter. Supposing an opacity in the lens to have a power of reflecting light falling almost perpendicularly upon it equal to that of the fundus oculi, the former would appear dark in comparison with the latter, if the illuminated area of the fundus were smaller than the area of the pupil; because the fundus would in that case be better illuminated than the opacity, and the observer would in general see each with nearly its proper brilliancy, provided the pupil of the observed eye were somewhat larger than his

own."

"In all cases in which the observer seeks to draw conclusions from the colour of objects seen within the eye, he must remember to make allowance for the quality of the light by which they are illuminated, and which reaches his own eye after undergoing various modifications consequent upon its reflection from, and transmission through other bodies, besides those which it renders distinctly visible."

"It will be found that objects seen by means of the ophthalmoscope generally present a lighter shade of colour than they do when seen by ordinary daylight, especially if the direct method is employed."

"The principles upon which we may determine the state of focal adjustment of the observed eye have been already discussed. The importance of the ophthalmoscope used for this purpose in military and medico

The reader will find observations on this subject by Mr. Streatfield. Ophthalmic Hospital Reports, No. xi.

legal practice, has been pointed out by Professor E. Jager of Vienna.* He refers to a circumstance, which may rather embarrass the observer in examining hyperpresbyopic eyes in the direct manner, viz., that in extreme cases the apparent magnitude of the image of an object, such as the papilla, may not exceed a third or a fifth part of what it appears in a normal eye. A much larger area is then seen, and this circumstance may add to the difficulty of illuminating hyperpresbyopic † eyes, referred to in Part II. The illumination may or may not be fainter than it is in a normal eye, according to the mode in which it is accomplished, and according to the cause of the hyperpresbyopia, whether dependent on absence of the lens, &c., or on shortening of the axis of the eye; but the area illuminated will always appear smaller than of equal dimensions in a normal eye, and it will seldom occupy the whole of the observer's field of vision."

"Apparent motions of objects situated in different planes within the eye, are often very difficult to distinguish from real ones. They may depend on motions of the eye observed, or on motions of the observer, or the biconvex lens held in his hand. The apparent changes in the position of objects caused in this way may be regarded as an exaggeration of those observed in looking at objects from different points of view under ordinary circumstances; except that in the direct mode of examination, it is the most distant objects which appear to move most rapidly, instead of the nearer ones, as is always observed in nature, and generally in the inverted image."

REVIEWS AND NOTICES OF BOOKS.

Contributions to Bone and Nerve Surgery. By J. C. NOTT, M.D., Professor of Surgery in Mobile Medical College. Philadelphia: J. B. Lippincott & Co. 1866.

As was to have been expected, the late unhappy struggle has, from the number of the casualties that occurred, afforded a wide field for the improvement of Surgical and Medical Science. but more especially the for

mer.

Now that it has terminated, the laborers are putting together the facts, and drawing such deductions as seem to them to flow from them. Among the few that have already appeared, this unpretending little volume of about one hundred pages is certainly not the least valuable. Opening

Der Augenspiegel als Optometer, österr. Zeitschrift für practische Heilkunde, March, 1856. Hypermetropic. Hypermetropia.

with a brief summary of the views advanced on periostitis, endostitis, ostitis, caries, necrosis, &c., he passes in the second part to give such views on bone and nerve surgery, as cases that came under his notice, while an active participant in the war, seem to warrant. Before noticing one or two things in the second part of the work, we would allude in favourable terms to a method of operating to relieve the great pain of acute periostits when you have reason to believe suppuration has not occurred, which is, we believe, alone recommended by Dr. Nott. Gross and other surgical writers recommend, whether fluctuation can be detected or not,when great pain exists, to cut down through the skin, and relieve the pent up matter. Dr. Nott says: "In periostitis, accompanied by severe pain and effusion of lymph and serum, with a tendency to suppuration, it is proper to make a small opening, at the lower part of the swelling, introduce a probe-pointed knife flatwise, pass it along between the skin and periosteum to the upper border of the swelling then turning the cutting edge towards the periosteum, and while withdrawing the knife.divide the periosteum subcutaneously down to the bone, through the whole extent of the swelling. When we are sure suppuration has occurred, it is better to make a free incision through the skin." In the second part of the work, alluding to gun-shot injuries, he says: My general rule has been thus; if a patient comes to me two or more months after a gun-shot injury, with a fistulous opening, unless contraindicated by an inflammatory condition of the part or an unhealthy condition of the system. I cut down boldly in the direction of the sinus, laying it opening to the bone, and then introduce my finger and explore it fully so as to ascertain, certainly what is the condition of the bone, and whether I am justified in removing the dead portion ****** In the majority of cases I find balls, clothing or other foreign bodies, and the patient is relieved at once by the removal." Dr. Nott, in alluding to what sometimes occurs in flap operations, but more particularly in circular operations according to Gross-viz., exposure of the bone, either from sloughing or from sufficient covering not having teen left, says:

"In those cases where the bone projects from the stump, the inexperienced surgeon is often tempted to interfere, not only unnecessarily, but injuriously with the operations of nature. I have been often consulted to know whether it is not best to saw off the projecting bone; but though a contrary opinion has recently been advanced by an army surgeon, I unhesitatingly say no. Where a bone projects from an open, suppurating stump, under any circumstances, it will require at least a month, and probably six or eight weeks, before the stump can be healed, whether the bone is on or off. Experience teaches that nature will amputate the bone, and generally at a very good point, by the time the rest of the wound