502 BOOK REVIEW believe they are indicated. I am not partial to the extracapsular method but use both methods, and I am thus in a position to compare the two. For this reason I can state positively that the postoperative re­actions are comparatively less marked after extracapsular extraction. As regards the suggestion that excessive pressure may be exerted by Mexican surgeons who use the intracapsular method, I may state that in my own work I do not exert any pres­sure at all. Furthermore, mere tension on the fibers of the zonule is capable of caus­ing increased ciliary reaction. As regards the question of waiting for maturity, in my opinion most patients show so much difference as to the stage of development of the cataract in the two eyes, that they are still able to use the unoperated eye after extraction of the mature cataract from the other eye. Even where the prog­ress of the two eyes is more synchronous, there is no objection to waiting for full maturity in the second eye, and this will

imply that each of the cataracts can be operated upon at maturity.

(Signed) M. de Rivas Cherif, Mexico, D. F .

X-RAY STUDIES I N RETINOBLASTOMA

In the January, 1947, issue of the JOURNAL, two cases of retinoblastoma are reported. I t is not clear whether X-ray studies of the affected globes were made. Possibly if the technique of Pfeiffer, Archives of Ophthalmology, 1936, volume IS, May, pages 811-821, had been used, the finding of opaque areas of calcifica; tion might have led to an earlier diagnosis.

The procedure recommended by Dr. Pfeiffer can be employed by any careful roentgenologist, as it consists only in X raying the globe to demonstrate intraocu­lar opacities. I recall two cases in which such X-ray studies furnished decisive information.

(Signed) Loren Guy, New York, New York.

B O O K O P T I Q U E I N S T R U M E N T A L E . By

G. A . Boutr)'. 540 pages. Paris, Masson et Cie., 1946. It is refreshing to noté that so admir­

able and interesting a book and one so beautifully printed can be produced in war-torn Europe. This book is based on a series of lectures to students and deals with the entire subject of instrumental optics, as distinguished from geometric optics, except computation. That subject is dealt with in a separate course. Optical principles are thoroughly elucidated with­out mathematics beyond the capability of an ophthalmologist. However, the oph-

R E V I E W thalmologist will read the book, for the most part , because the subject delights him, and not to increase his usefulness in his profession.

There are two chapters on the optics of the human eye and the corrections of the optical defects. The analysis of resolving power is discussed with particular clarity and interest. The last section of the book consists of a number of monographic chapters on individual optic instruments— lamps, the compound microscope, tele­scopes, binoculars, and photographic in­struments.

F . H . Haessler.