654 PHOTOGRAMMETRIC ENGINEERING

graith (10) suggested that hepatic venousconstriction may be intimately concernedin the control of the blood flow through theorgan and in the pathogenesis of lesionswhich appear in various disease states.

I t would appear possible to use a similarprocedure with laboratory animals tomeasure the variations in the width of thelarge blood vessels, thus eliminating thevariations caused by the contrast agentsin use at present.

It thus seems clear that problems ofboth theoretical and practical importancecan be investigated with photogrammetricmethods; intimate cooperation betweenmedicine and technology in this fieldshould be of benefit to both.

BIBLIOGRAPHY

1. HaIIert, B. and Fagerholm, P.O., "Sum­mary of the Photogrammetric Developmentin Sweden during the Period 1948-1952"Fotogr. Moo. Vol. II, No 2, 1952.

2. Adams-Ray, ]. and Hjelmstrom, P.,"Mecanisme de I'action du Blocage Sym­pathique sur L'oedeme Traumatique."Presse Med. 59:1206, 1951.

3. Bjorn, H. and Lundquist, C. "A Photo­grammetric Method of Measuring theVolume of Facial Swellings." To be pub­lished in J. Dent. Res.

4. Knisel, M., "An Annotated Bibliographyon Sludged Blood." Postgrad. Med. 10: 15,1951.

5. Sjostrand, F., Personal communication.6. Hagberg, S., Hjelmstrom, P. and Adams­

Ray, J., "Registering av Andningsrorelserav Brostkorg och Bukvagg med Fotogram­metrisk Metod. Nord. Med. (in press).

7. .Berghagen, N., "Photogrammetric Princi­ples Applied to Radiodontia." Thesis.Stockholm 1951.

8. Adams-Ray, ]., Hagberg, S., tIjelmstrom,P. and Olsson, S. E. "A Roentgen Stereo­photogrammetric Method for MeasuringVolumevariations of Organs in the LivingAnimal." To be published in Acta Phys.Scandinav.

9. Wiggers, L., "Physiology; in Health andDisease." 4th Edition. Lea & Febiger.Philadelphia, 1946.

10. M'aegraith, B., "Liver Injury." HoffbauerF. W. Editor. Trans. Tenth Con/. New York,Josiah Macy Jr. Foundation 1951 (p. 181).

STEREOPHOTOGRAMMETRY AND STUDIESOF MOVEMENTS*

Prof. Dr. M. Zeller, Swiss Federal Institute of Technology, Zurich

F OR years the manual movements in of 40 cm. was used by which a plotting ac­certain working processes have been curacy of about 1 mm. on the scale of 1:2

taken cinematographically or by the so- was obtained for taking distances up tocalled light point's process. By both about 4 mm.methods we obtain a clear pic;ture of the In studies of movements another lightmovements executed; they do not, how- signature has to be chosen for every work­ever, permit obtaining a sufficiently ac- ing course. This is obtained by using ancurate determination of their form and automatic interrupter with variable in­especially of their strewing. For the study tervals. This is necessary, since the' coursesof the economy of working processes, need of the lamps belonging together must beexists for an exact knowledge of the spatial established beyond a doubt, within acurves of the single movements and their range where different movements arestrewing, and consequently the possibility continually crossing.of a comparison with other working dis- Furthermore the first experiments havepositions. Only this possibility of compari- shown that from a series of about 24 work­son permits ascertaining the most favora- ing courses on one pair of photographs it isble working conditions with regard to adVIsable to take out only 3 to 4 repeti­length of way and form. For the study of tions in. certain intervals. Thereby we ob­the movements, the operator who was tain also a better mean value of the move­examined was provided with incandes"cent ments and a more reliable picture of thelamps on both hands, and also on the head strewing. The photographs were taken in aand shoulders. For the task in question the feebly darkened room, the shutter of the"Wild" Stereo-Camera of a basic length stereo-camera remaining open while taking

* Summary of the treatise in the Congress Number VIII, 1951/52,4 of "Photogrammetry."

SYMPOSIUM: NON-TOPOGRAPHIC PHOTOGRAMMETRY 655

3 to 4 repetitions of a working course, andwith the light signs altered for every newworking course by automatic connections.This method permits a reliable identifica­tion of the various working movementswhich is quite impossible with the usuallight point's process. The stereoscopic ob­servation offers, furthermore, some veryconsiderable advantages as against monoc­ular observation, since only in the formermay the differences of depth also be ob­served.

The plotting was executed with the"Wild"-Autograph A 5 with the scale of1 :2. The plotting permits also determiningthe way passed over in units of time. Theseexperiments led for instance to the follow­ing statements.

1. The greater the distance run, thegreater the velocity and the straighterthe course of the movement.

2. The shorter the distance run, thesmaller the velocity and the vasterthe course of the movement.

3. The plotting of the courses of themovements further shows, that theright hand sometimes has to wait forthe left, and that there occur shiftingsof time between the two hands whichare caught up at the fix points ofmovement.

4. The experiments confirm the funda­mental rule, that human work hasthe tendency to rhythmical move­ment.

There should be no dou bt that the stereo­scopic plotting of movements opens upquite new perspectives for the scientificstudy of working processes and for thedetermination of working depositions giv­ing maximum results.

A NEW METHOD FOR INTRA-ORAL RADIOGRAPHYlNils Berghagen, D.D.S.2 and Petter Hjelmstrom, Civil EngineerS

T HERE exists in the science of odon­tology a real need of an accurate

method for following physiological andpathological processes in the jaws with theaid of radiography.

The radiographic material at the dis­posal of the practicing odontologist doesnot, unfortunately, always possess themost desirable properties, so that the op­portunities of performing good diagnosesin odontology, and particularly in oralsurgery, are much restricted. In mostcases the diagnosis is made and the the'rapydecided from clinical examinations andfrom the study of' single radiographs.These single pictures can, however, be ofgreat value when the object is to estimatechanges in a particular region of the jaw,provided that one works on the principleof serial identical radiography. The term"serial identical radiography" should notmislead one into thinking that it is a ques­tion of identity in the mathematical sense.

I t is in fact a question of a greater or lesserdegree of geometrical similarity in orienta­tion.

Rather than to study single pictures,however, we have found it preferable toexploit the advantages of stereo-radiog­raphy. After interpretation of 3,000 radio­graphs taken by our method we havefound that a comparison between a singlepicture and a stereo-pair taken in the cor­rect manner has proved that the latter issuperior. The information yielded by thestereo-picture, despite shortcomings in­herent in the character of the radiograph, is

.always more detailed than that given bythe single picture. Even if, on account ofthe distribution of contrasting points inthe object, a correct space conception ofall such points cannot be obtained, thestereo-picture can be said to reproduce, insome degree, the three-dimensional effect.

So long as stereo-radiography is per­formed in accordance with the theoreti-

1 The contents of this paper are based on experiments treated in the thesis "PhotogrammetricPrinciples Applied to Intra-oral Radiodontia," by Nils Berghagen, Stockholm 1951, and on laterdevelopments. A more complete account will appear in Acta Odontologica Scandinavica, Volume 11,1953.

2 Associate Professor in Oral Surgery at the Royal Institute of Dentistry, Stockholm, Sweden.3 First Assistant at the Division of Photogrammetry, Royal Institute of Technology, Stock­

holm.