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RUDIMENTARY SPINA BIFIDA. 



In several adult cases reported by Els a history of symptoms of spina bifida, 

 appearing after more or less protracted trauma, is recorded. It is quite probable 

 that in adults mechanical agents act more frequently as secondary than as primary 

 etiololgical factors, producing a clinical spina bifida, as differentiated from a solely 

 anatomical condition. In early childhood, however, the possibility of such factors 

 being primary must be taken into account, as the vertebral dorsal arches are at 

 that time incompletely ossified. 



We are not as yet far enough advanced to determine definitely the correlation 

 between time and etiology in such a variation as is here dealt with, but it is hoped 

 that a small amount of speculation, in an effort to supply a preliminary orientation 

 in regard to this factor, will be pardoned. It would seem that during prenatal life 

 the organism is more sensitive to metabolic disturbances, and that these would have 

 greater effect upon form than similar factors acting at a later time. On the other 

 hand, the indiv dual would appear to be slightly more subject to mechanical dis- 

 turbances, secondary, perhaps, to metabolic disturbances, resulting in slight changes 

 of normal growth sequences, during early postnatal than in either prenatal or adult 

 life. So, while one can not make positive statements as to either the time or the 

 character of the disturbances producing the different types of spina bifida, there is 

 the possibility, when the defect is a limited one, that its presence may have been 

 partially due to mechanical factors occurring during childhood. Where the process 

 is more extensive, however, such a possibility disappears, and in these there must 

 have been a more fundamental metabolic disturbance acting at an earlier date. 



Before closing, mention should be made of the fact, brought out by Frets, 

 that in six-segmented sacra the percentage of lower closures (Si) of the hiatus of 

 the sacral canal is greater (34 per cent) than in those with 5 segments (5 per cent) ; 

 and that the percentage of reduction in the posterior arch of Si is somewhat ower 

 (21.5 as opposed to 34.0) in 5-segmented than in 6-segmented sacra. Evidently the 

 caudal extent of the sacrum is associated with a corresponding tendency towards 

 posterior closure of the vertebral arches in this region the longer the sacrum, the 



lower the closure of the hiatus. 



SUMMARY. 



The condition of incomplete closure of the vertebral posterior arches is present 

 in the different regions of the spinal column in the following order of frequency: 



