The helical structure of the human umbilical cord has been studied on 528 full-term cords from normal deliveries, 18 cords from aborted and developmentally normal fetuses with a CR length of 1.2–19.5 cm, and 10 cords from monozygotic twins. In order to resolve the discrepancy in the nomenclature of the twist direction, a method has been suggested which takes into account the direction to which the fetus must have rotated to produce the twist. The incidence of the right helical pattern was 64.58%, of the left helical pattern 15.15%, and of the mixed patterns 17.43%; the twists were indeterminate in 1.89% and absent in 0.95% of the cords. Details of the mixed patterns are listed. The number of the uniform right twists ranged from 1 to 29 (7.5) and that of the left twists from 1 to 19 (6.7). There exists an exponential relation between the number of the twists and the ratio between length and thickness of the cords. The twists begin to appear during the early part of the 8th week, and their final number is possibly attained soon after the 9th week of development. In view of the absence of concordance in monozygotic twins, the helical nature of the cord is possibly controlled by factors which may be partly genetic and partly environmental.

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The calvarial defect in human anencephaly has been studied on 21 anencephalic skulls in all of which the defect extended into the vertebral column. Based on the boundaries of the defect, a nomenclature of the anomaly has been proposed that is simpler, more scientific, and more informative than previous ones because it expresses the precise extent of destruction of the cranial vault. In the present study, the defect was "fronto-occipito-vertebral" in in 71.4%, "occipito-vertebral" in 23.8%, and "parieto-occipito-vertebral" in 4.8% of cases. The morphologic details of the cranial bones bounding the calvarial defect have been described.

Single umbilical artery associated with multiple anomalies is described in three stillborn human fetuses. Detailed study of the abdominopelvic arteries showed replacement of the abdominal aorta below the origin of the superior mesenteric artery by the umbilical artery in all three specimens. This finding greatly helps in solving the age-old riddle of the cause-effect relation between the umbilical anomaly and its associated defects. Single umbilical artery can give rise

Spinal retroflexion has been studied in five stillborn human fetuses having craniorhachischisis. The findings show that retroflexion in this variant of anencephaly can be classified into severe, moderate and mild forms. The three grades can be differentiated from one another by the direction of the face, shape of the mentothoracic junction, extension of hairline on back, radiographic abnormalities of the spine, and the diaphragmatic defects. It is discussed that, though the anencephalies with severe or moderate degree of cervical retroflexion resemble iniencephaly in their features of spinal retroflexion, those having mild retroflexion are contrasted and should not be categorised with iniencephaly. It is suggested that for precision the term ‘spinal retroflexion’ should be used after duly prefixing it by an appropriate word (severe, moderate or mild) indicating the degree of retroflexion observed.