Con il 1956 si apre il V volume della nostra Rivista e si compiono cinque anni da quando abbiamo pubblicato il libro « Studio dei Gemelli ». Una vasta famiglia di autori, ed una più vasta di lettori, si è raccolta attorno ad « Acta Geneticae Medicae et Gemellologiae » la quale, unitamente al libro, ha valso a rinfocolare l'attesa e l'impegno attorno agli studi gemellari, ed a raccogliere un materiale di cospicuo interesse.

Per sottolineare questa circostanza riprendiamo il profilo storico della gemellologia che abbiamo tracciato in un capitolo di « Studio dei Gemelli » per integrarlo con alcuni dati recentemente acquisiti, non senza notare che, in genere, questo assunto non coincide con quello di aggiornare il lettore con i progressi della gemellologia, perchè altra cosa è l'apporto scientifico, a cui attende periodicamente la Rivista, ed altra cosa l'elaborazione storica del pensiero scientifico.

Quest'ultima richiede, fra l'altro, una certa prospettiva nel tempo, cioè una distanza che consenta di attribuire ad ogni apporto il valore che effettivamente e definitivamente gli compete per accordarlo con le linee di sviluppo del pensiero scientifico.

Das fotografische Bild eines menschlichen Kopfes ist eine flächenhafte Wiedergabe einer Vollplastik. Wenn eine solche Aufnahme wissenschaftlichen Zwecken dienen soll, muss man von ihr erwarten, dass sie alle Formmerkmale richtig erkennen lässt, so dass aus dem flächenhaften Bild die richtige Plastik herausschaut.

Bei Familienuntersuchungen und beim erbbiologischen Aehnlichkeitsvergleich, wie ihn der Anthropologe durchführt, spielt die Beurteilung morphologischer Merkmale nach Lichtbildern eine erhebliche Rolle. Eine richtige bzw. falsche Beurteilung von Einzelmerkmalen an einer Kopfaufnahme kann weittragende Bedeutung haben. Um eine Basis für einen brauchbaren Vergleich von Bildern und eine richtige Beurteilung von Merkmalen am Lichtbild zu schaffen, muss eine gewisse Normierung in der Aufnahmetechnik eingehalten werden, auf die im Schrifttum schon oft hingewiesen wurde (z. B. Mollison, Th., 1910, Arch. Anthrop. N. F. Bd. 9, S. 305-321; Martin, R., 1925, Anat. Anz. Bd. 59, Nr. 22/23, S. 529-538; Rodenwaldt, G., 1935, Archäol. Anz. S. 354-363). Alle Fehler, die sich nur zu leicht bei fotografischen Aufnahmen einschleichen, müssen erkannt und nach Möglichkeit beseitigt werden.

An Hand von einigen Lichtbildern aus der praktischen Arbeit des Anthropologen soll auf solche Fehler aufmerksam gemacht werden. Hierbei müssen vor allem beachtet werden die Einstellung des Objektes zur Kamera und die Beleuchtung.

An African woman of about 40 years old reported to the out-patients' department on 31st January 1955 because of nausea and vomiting, with amenorrhoea of three months duration. Examination revealed a 2-months' pregnancy. She had six normal deliveries of which three children were still living.

On 3rd February she reported again, complaining of stomach-ache and diarrhoea. The stool examination showed some leucocytes and erythrocytes, but no amoebae, cysts or parasitic ova. On 23rd February the woman again reported, this time with a simple pharyngitis. She came again on 29th June for pre-natal examination and treatment. She had no complaints and was seen to be about 32 weeks pregnant, with a moderate degree of hydramnios. The foetal heart was inaudible.

On 1st August she was admitted to hospital in labour. The membranes were intact, the cervix fully dilatated and presentation was occipito-anterior of the vertex. Artificial rupture of the membranes released only a small amount of amniotic fluid, but labour proceeded normally with the usual quantity of fluid accompanying the birth. Immediately this child was born another bag of waters presented, which was ruptured to release about six pints of amniotic fluid. A second baby now presented by the breech and was delivered by Bracht's method. We noticed at once that this second baby was affected by mongolism.

Twin research affords an opportunity to study the interplay of heredity and environment. For this reason, twin research is of special interest in the study of physiology of exercise. Genetically, identical twins are the same individual in duplicate because they are the product of a single fertilized egg which splits in half to form two individuals. Non-identical twins are different individuals who through chance were born together. They originate from two different eggs.

In non-identical twins, physique may differ significantly because each partner possesses his own hereditary endowment (fig. 1). By contrast, identical twins represent two editions, so to speak, of the same body type (fig. 2). The degree of correspondence of morphological body features in identical, as against non-identical, twins has been statistically assessed by Newman, Freeman, and Holzinger (Twins, A Study of Heredity and Environment, Chicago, 1937).