ENCEPHALOCELES AND OTHER ABNORMALITIES. 107 



The central canal, as such, is absent. Throughout the extent of the cord it 

 is changed to a flat space following the contour of the vertebral column, whose floor 

 is the cord and whose roof is partly the same cord inverted, partly the inverted 

 floor of the fourth ventricle, and partly cerebellar tissue. 



This fragmentary description of the central nervous system leaves much to 

 be desired. It would have been especially desirable had we been able to present 

 a clear picture of the relationships of the meninges. The main conclusion which 

 can be drawn from its study is that the chief disturbance here evidenced is primarily 

 one of distortion, rather than of absence or real lack of development of nerve- tissue. 



CONCLUSION 



The exterior alone of such a specimen as this certainly presents striking evi- 

 dence that an organism can undergo most serious disturbances and yet maintain 

 a definite though limited growth balance ; but in order to ascertain in detail exactly 

 what constitutes the limitations of this equilibrium more intensive study is 

 necessary. A rather interesting series of anomalies is the result of such a study in 

 this case. It may be noted that these anomalies are centered about the axis. The 

 bony parts, the central nervous system, certain adjacent muscles, and overlying 

 areas of integument share profoundly in this disturbance. Subsidiary disturbances 

 of development are evidenced in a split soft palate and a one-lobed right lung. 

 These facts, in addition to supplying a clearer knowledge regarding the individual 

 specimen, contribute their small share in providing data for the better understanding 

 of certain general problems of development. Classifications and analyses included 

 in such subjects as osteology, myology, and organology can not be regarded as 

 complete until they contain a comprehensive picture of teratological phenomena. 

 This is almost entirely lacking at present. The teratological material has been so 

 scanty that any satisfactory correlation of it has been impossible. 



Up to fairly recent times teratology was considered an isolated science; it was 

 thought that the laws applying to most natural phenomena were not applicable to 

 its conditions, that it could not learn from or contribute to the normal sciences. 

 Studies of the past half century have entirely reversed this view. Teratology to- 

 day has for its basis the same fundamental sciences of chemistry, biology, and 

 physics as has those sciences whose subject-matter deals with normal phenomena. 

 It is constantly learning from these latter sciences, and in turn has been able to con- 

 tribute suggestions on points of analysis or exposition regarding puzzling phases of 

 normal development. 



The necessity of furthering our knowledge regarding the etiological factors of 

 specific abnormal conditions has been considered. Material at such an advanced 

 stage of development as this specimen can contribute but little along this line. . We 

 can not determine by means of it the primary defect, nor again, except in a very 

 general way, a chronological picture of the early processes. We must turn to em- 

 bryological material and to other than morphological methods to obtain such 

 knowledge. 



