136 CORRESPONDENCE

rially reduce the weight, an important factor for the traveler. In addition they make color readily available and there can be no doubt of the value of color in projection slides.

If the 2 by 2-size slides are used, they must be photographically good, for poor slides of this type, when projected, tend to exaggerate the defects that may be present. There are certain fundamental principles that must be considered if the projection of illus­trations is to be effective. Anything that tends to detract from the data the slide is attempt­ing to point out must be avoided.

If color slides are used they should be properly exposed; also, they must be in focus, as colored illustrations out of focus are very uncomfortable to the observer. They should be mounted in glass so that they can be easily focused and the focus maintained during projection. The cardboard mounts furnished by the processors of color are un­satisfactory as the film has a tendency to buckle when it becomes heated. Glass slides also protect the films against damage. It is well to remember that one poor picture may detract so much that the good ones are for­gotten.

Care should be taken that the illustrations are projected right side out and not "up side down." If the photograph of a drawing is projected with the artist's name "up side down" and backward the audience has a tendency to attempt to decipher the name rather than to observe the data presented.

Slides should be clean: finger prints, par­ticles of dust, and smears detract a great deal.

In the use of slides, it is important that data projected be confined to the area of the slide normally used; the masks for both types of slides are standardized as to the space used for projection. If this is not observed the author may find that the most important part of the slide is off the screen. This hap­pened a number of times at the recent meet­ing. The above precaution is especially impor­tant if 2 by 2 slides are used.

When typing is used, a common mistake is to include so many lines that it is not legi­ble. In the preparation of typing for slides,

a new ribbon should be employed and not over 12 lines double spaced used. Another fault is attempting to get so much material on a single chart that when it is projected it is not readable.

When high-power microphotographs are used, they should always be preceded by a low-power projection so that the audience can orient itself.

Slides to be used at a medical meeting should be prepared well in advance so as to allow sufficient time to replace any defective illustrations.

When the slides are given to the projec­tionist, they should be in proper order and be properly marked in the upper right hand corner by a small paper disc or star. In the preparation of Kodachrome slides, the dull surface should be toward the screen and the slide should be upside down. When the slides are projected, the author should speak from the slide or glance at the slide to be certain that it is in focus since there is a tendency among projectionists to set the instrument at one point and not bother to readjust the focus for various slides. It is usually essential that the author point out the important features of the illustration.

If illustrations are to be used during the presentation of a paper, they must pertain to the subject, must be clean, in good focus, and readily readable if the audience is to be held, otherwise, with the lights off, a warm room, and poor slides, there is a tendency to take "40 winks" while the author drones on.

Frederick C. Cordes.

CORRESPONDENCE EFFECT OF RETROBULBAR ANESTHESIA ON

OCULAR TENSION AND VITREOUS PRESSURE

Editor, American Journal of Ophthalmology:

In your October issue I read a paper by Dr. Harold Gifford, Jr., entitled "A study of the effect of retrobulbar anesthesia on ocu­lar tension and vitreous pressure."

I wish to make a few comments on the paper. Some years ago I made a study of

BOOK REVIEWS 137

"Retrobulbar anesthesia effects and ophthal-motonus," issued in the Brazilian review, O Hospital, October, 1945.

In the material dealt with, the tension was taken before any anesthetic was used, except one drop of 0.5-percent tetracaine, and then, in the first group, after five-percent cocaine-adrenalin repeated instillations; in the sec­ond group, after cocaine (five-percent) in­stillation ; in the third group, after retrobul­bar anesthesia with four-percent novocain-adrenalin; and in the fourth group, with retrobulbar injection of novocain (four-per­cent) without adrenalin. I saw a tension-lowering effect in each group that was greater when adrenalin was added. I con­cluded also that the lowering effect of co­caine-adrenalin instillation was greater than that of retrobular injection of four-percent novocain-adrenalin. The lowering appeared in 4 to 5 minutes after the injection.

(Signed) Evaldo Campos, Rio de Janeiro, Brazil.

TOXICITY OF T.E.P.P. Editor, American Journal of Ophthalmology:

Since preparing a report* on the ocular evidence of toxicity from tetraethyl pyro-phosphate (Parathion as used for crop dust­ing) , I have been informed of several deaths from this substance.

In discussing this report, Dr. Wilson T. Sowder, state health officer, said that spray­ing with T.E.P.P. had been so effective against insect pests, and had so improved the crops, that it would not be discontinued, but the crop dusters must take proper precau­tions and doctors must be familiar with toxic symptoms and be prepared to treat any case of T.E.P.P. poisoning as an emergency.

T.E.P.P. has the same pharmacologic ac­tions as D.F.P., and the eye signs of T.E.P.P. poisoning are recognizable early. The anti­dote is atropine (1/100 gr.) repeated until dilatation of the pupils occurs. In addition to

* Read before the Southwestern Medical District, Sebring, Florida, October 27, 1949.

the miosis and ciliary spasm (lens fixed for near vision), the intraocular pressure will be found to be lowered.

It is reported that there may be striated muscle fasciculations, increased gastrointes­tinal tone with abdominal cramps, diarrhea, nausea, vomiting, perspiration, lacrimation, salivation, restlessness, bradycardia, cardio-spasm, complete auricle ventricular disso­ciation, constriction of bronchial muscles, increased secretion of bronchial glands, con­vulsive seizures that may be epileptiform.

Death may occur from bronchial spasm, overstimulation of autonomic effector cells, from central stimulation followed by depres­sion, or from stimulation followed by de­pression of striate muscles which, if death does not occur, may be followed by muscle paralysis as in Jamaica-ginger poisoning of the prohibition era. If the patient survives 24 hours he will live, hence the urgency for immediate treatment.

(Signed) Garland M.Johnson, Fort Lauderdale, Florida.

BOOK REVIEWS VOLUME IV*

Cui mens divinior, atque os Magna sonaturum, des nominis huius honorem.

Horace, Sat. (He alone can claim this name, who writes with fancy high and bold and daring flights.)

"I must apologize for the delay in the appearance of this volume, but six years of military service far from the study and the library have not been conducive to the com­pilation of a book of this type." (Note pic­ture above.)

"But it was in 1932 that the author ren­dered his greatest contribution to ophthalmic science. In this year the first edition of Vol­ume I of his Textbook of Ophthalmology appeared. This first volume alone, of more than a thousand pages dealing with the De-

* TEXTBOOK OF OPHTHALMOLOGY. By Sir Stewart Duke-Elder, K.C.V.O., M.A., D.Sc. (St. And.), Ph.D. (Lond.), M.D., Ch.B., F.R.C.S., F.A.C.S. (Hon.), D.Sc. (Hon. Northwestern). St. Louis, the C. V. Mosby Company, 1949. Price, $20.00.