460 SK1AGRAPHIC RESEARCHES IN TERATOLOGY. 



spinal column. There is an extraordinary degree of distortion of the ribs, which is 

 probably secondary to the malposition of the viscera. 



The flexure of the spinal column in these .cases should be compared with the 

 sigma curve of the column of primitive segments in the dorsal region of the early 

 embryo (Manual of Antenatal Pathology, vol. ii, figs. 10, 11, and 12). 



Fig. 28, Plate XII, is taken from a specimen which has been described in the 

 second volume of the Manual of Antenatal Pathology (fig. 75, pp. 518, 519). It 

 represents anencephalus and exomphalos, with an extraordinary degree of curvature 

 of the spinal column. There is spina bifida affecting almost the whole vertebral 

 canal. The monstrosity was born in the practice of the late Dr C. E. Underhill of 

 Edinburgh, and the details are given in the Transactions of the Edinburgh Obstetrical 

 Society (vol. xvii, p. 278, 1892). The X-ray photograph shows that the lumbar 

 spine is fairly straight, whilst there is marked kyphosis of the dorsal, and lordosis of 

 the cervical, regions. 



Fig. 29, Plate XIII, is somewhat similar to the preceding, but the spinal curvature 

 is still more marked and more extraordinary. The fetus was born in the practice of 

 Dr Ballantyne of Dalkeith, and details are given in the Transactions of the Edin- 

 burgh Obstetrical Society (vol. xvii, p. 241, 1892). The X-ray photograph shows 

 very clearly the extreme degree of spinal curvature. 



Fig. 30, Plate XIII, is somewhat similar as regards the curvature of the spine, 

 but there is no exomphalos. The specimen came from Dr Duff of Helensburgh, and 

 details are given in the Transactions of the Edinburgh Obstetrical Society (vol. xx, 

 p. 13, 1895). The X-ray photograph shows the extraordinary dorsi-fiexion of the 

 head and the abruptness of the S-shaped curve of the spine. 



Group D. 



( Characterised by the presence of an excess of determifiants. ) 



In fig. 31, Plate XIV, a good example is presented of the arrangement of the 

 bones of the hand in a case of dichirus, and in fig. 32 in the same Plate are shown 

 the doubled thumbs from a case of symmetrical Polydactyly. 



Fig. 33, Plate XV, is a radiograph of thoracopagous united twins that occurred in 

 the practice of Dr Robert Stewart of Edinburgh. The external appearances are 

 given in the Manual of Antenatal Pathology (vol. ii, p. 657). They had to be 

 separated from each other in order to make their birth possible. The most marked 

 feature is the extreme distortion of the spinal column in each. This case is of con- 

 siderable intrinsic interest, and perhaps it may be explained by assuming that the 

 determinants were doubled and segregated at an early age. Each ordinary deter- 

 minant is thus represented by two separate determinants. If the process is complete 

 for all the determinants, one gets " identical twins" ; if it is partial, the result is the 

 formation of complete or partial double monsters. 



