From the Mermaid to Anal Imperforation: The Syndrome of Caudal Regression.

If the mermaid legend evokes more of mythology than of pathology, its origin very probably lies in ancient observations of certain types of human monstrosities. Human sirens are not as rare as is sometimes thought; I have been able to examine two cases within the past year, and during that time I have been told of several others. I shall talk today of the usual findings and attempt to draw certain wider conclusions. The fusion of the inferior limbs, the symelia (Fig. 1), which constitutes the characteristic element of the malformation to the observer, is not the only abnormality in these cases (Potter. 1952). The more constant findings in monsters of this general type may be summarized as follows (see Table 1): 1. Flexion and inversion in external rotation of the lower limbs. 2. Anomalies of the lumbar and sacral spine. 3. Imperforate anus. 4. Agenesis of the kidneys and urinary tract. 5. Agenesis of the internal genital organs, with the exception of the gonads. The visceral anomalies are constant and uniform. It is these anomalies which are incompatible with life, while the symelia is the least grave and the more variable of the malformations presented by the siren. There are even sirenoid monsters in whom