mercury break, which can be used with a current of 275 volts off the main.

*

Caldwell, of New York, who has had extensive experience in Röntgen-ray examination of the sinuses, states that :

I. A frontal sinus exposure will require from twenty to fifty seconds with a tube which, for a skiagraph of a wrist or hand, will require one second or less. To lessen the strain on the tubes as much as possible, the fastest plates obtainable should be used.

FS

B

Fig. 111. To show A-the good position-the principal ray passing through the skull above the occipital protuberance to the frontal sinus. B-the bad position for the tube, as the principal ray passes right through the occiput and base of skull before it reaches the sinus.

2. Large tubes with eight-inch bulbs and very heavy targets are to be preferred to the more usual tubes on account of the longer exposures required in sinus work.

3. The best penetration is about 9 or 10 on the Benoist scale, for while the rays must be of high enough penetration to pass through

*Laryngoscope, Nov., 1908.

Fig. 112.-Two photographs of a model showing the effects of changing the position of the tube with reference to the skull. In A. the principal angle is approximately 25°, and it will be seen that the rays passing through the frontal sinus are not obstructed by irregular parts of the base of the skull. In B, the principal angle is too small (about 5): therefore the shadows of the parts of the base of the skull would be superimposed upon those of the sinus.

1. Very large frontal sinuses with many septa. Fluid is shown in right frontal and right maxillary sinuses, the fluid being pus.

2. Frontal sinuses rather large, but contain no fluid.

3. Asymmetrical frontal sinuses. In this case transillumination was misleading. The principal angle is a little too small, and the shadows of the petrous bones are shown over the lower third of the orbit.

4. Left frontal and both maxillary sinuses filled with pus. Principal angle a little too small for best results. CALDWELL.

the skull and brain, rays of too high penetration will not give the contrasts that are necessary.

4. Developers giving density are to be preferred. His best results have been obtained with pyrogallic acid, next to which he prefers hydroquinone.

5. "In most cases the proper direction of rays, for the anteroposterior projection, may be obtained with sufficient accuracy by placing the tube so that the glabella, the parietal eminences, and the target of the tube are approximately in the same plane, the source of rays, of course, lying in the mesial plane of the skull."

6. The knowledge of the antero-posterior depth of the frontal sinus, obtained from the transverse projection, is often useful in arriving at a correct interpretation of the antero-posterior projection. If the sinuses are deep, the quantity of fluid they may contain is greater, and the shadows cast by the fluid will be correspondingly stronger. When the sinuses are very shallow it will sometimes be impossible to decide whether they contain fluid. It has been proved that an oedematous lining membrane will cast as dense a shadow as a collection of pus or other fluid containing the same amount of water; and this should always be borne in mind."

Caldwell has conveniently termed the principal ray that ray which passes through the skull in the mesial plane and pierces the centre of the glabella. The basal plane passes through the centre of the external auditory meatus and the centre of the glabella, and the angle between the basal plane and the principal ray Caldwell has termed the principal angle.

AFFECTIONS OF THE EYE-OCULAR AND ORBITALDUE TO INTRANASAL AND ACCESSORY SINUS

DISEASE.

As a consequence of the intimate anatomical relations of the orbit and nasal passages, eye complications are very frequently encountered in patients with certain diseases of the nose, and more particularly with suppurations in the accessory sinuses. These eye complications fall into four groups: (1) Reflex nervous affections; (2) Mechanical displacement of structures; (3) Direct septic infection of the orbit or its contents; (4) Traumatic ocular complications.

I. Reflex Nervous Affections.-As an example of the physiological association between the eye and nose we may recall the conjunctival