100 



RUDIMENTARY SPINA BIFIDA. 



In the present investigation 1,000 consecutive X-ray plates of the lumbar 

 region in white adults (over 18 years of age) were studied at the X-ray department 

 of the Johns Hopkins Hospital, as were also all the available cervical vertebrae in 

 the Division of Physical Anthropology at the U. S. National Museum at Washing- 

 ton. From the latter source over 600 atlases and more than 3,000 other cervical 

 vertebras were examined. The kindness of Dr. Baetjer, of the Johns Hopkins X-ray 

 department, and of Dr. Ales Hrdlicka, curator of the department of physical 

 anthropology, National Museum, is acknowledged with pleasure. 



As the osteological collection at tr - National Museum was studied mainly for 

 cervical vertebrse, no thorough record of sacral conditions was attempted. In one 

 group of 33 white skeletons, however, in which the sacrum was present with the 

 rest of the spinal column, 2 cases of completely open sacral canal were noted. One 

 of these was in a sacrum composed of 5 vertebrse; the other was also in a five-seg- 

 mented sacrum, but in this case L 5 was sacralized on the left side, and that verte- 

 bra showed also a bifid dorsal arch (fig. 5). In one six-segmented sacrum in this 

 group the dorsal arches were united only over S 3 and S 4 . In a similar group of 22 

 sacra from various American Indian tribes the condition of an entirely open sacral 

 canal was noted twice. 



Examination of the X-ray plates TABLE 2. Types of defective sacrum. 



showed 4 cases of completely open 

 sacrum in white males and 4 in white 

 females. These are given in table 2 

 and clinical aspects of the cases fol- 

 low on page 102. Unfortunately, an 

 accurate count was not kept of the 

 entire number of plates in which the 



whole sacrum showed plainly, so that these cases could not be used in calculat- 

 ing percentages, and the groups of whites and Indians just noted are too small to 

 be of statistical value. In the X-ray plates dorsal closure of the first sacral 

 vertebra was found to be considerably defective in 78 cases of white males (14.57 

 per cent) and in 53 cases of white females (11.39 per cent). This ratio is in 

 close accord with that of Adolphi (12 per cent), while that of Frets is much 

 higher (24.6 per cent). The possibility of difference of opinion on this point 

 should, however, be taken into account. One has to choose a rather arbitrary 

 standard of what constitutes a defective first sacral arch, since the transitions 

 from a fully formed arch to an incomplete one are so very gradual. The author 

 found the second as well as the first sacral arch to be defective in 4 cases (3 

 male and 1 female). Occurring with slightly less frequency than in the sacrum, 

 complete union of the vertebral posterior laminae is found in the last lumbar ver- 

 tebra in from 2 to 3 per cent of cases. In the 1,000 consecutive X-ray plates of 

 the lumbar region of white adults that were studied, it was found 12 times among 

 535 males (2.22 per cent) and 11 times among 465 females (2.38 per cent), giving a 

 total of 2.3 per cent. Table 3 shows its occurrence and association with other 

 defective vertebrse. The designation, last lumbar, has been used instead of L 5 or L 6 , 



