132 PATHOLOGY 



disease was due to endocarditis in fetal life was largely due to the 

 knowledge of the susceptibility of the malformed part to secondary 

 so-called chronic inflammation. This is true not only of the macro- 

 scopic conditions like those mentioned, but it also favors the idea 

 that incompleteness in the formation and the later development of a 

 part cause a local disposition to disease. But this is only one side of 

 the relationship between disturbances of development and disease. 

 Another, perhaps even more important, is that which treats of the 

 development of tumors on a basis of disturbance of development. 

 The tumors of undescended testicles, the origin of new formations 

 from displaced adrenal fragments, are as familiar to pathology and 

 as surely established as the occurrence of dermoid cysts, which can 

 only be explained on the basis of the history of development. The 

 well-known theory, according to which all tumors depend on dis- 

 turbances in embryonal development, still lacks sufficient proof. 

 Both pathologists and embryologists have been successful in showing, 

 however, that one tumor at least, the dermoid of the ovary, only 

 finds a satisfactory explanation in the presence of derivatives of all 

 three embryonal layers, thus indicating a very early disturbance of 

 development. 1 These tumors are closely related to malformations 

 and pass without sharp division into true monstrosities. The study 

 of all malformations, not only those due to impeded development 

 and which no one attempts to deprive pathology of, is not to be 

 separated from the study of normal development, for the origin of 

 malformations goes back to the earliest embryonal period, and not 

 only malformations of the whole body but anomalies of its single 

 parts can only be understood and their origin explained in the light 

 of normal developmental processes. 



On the other side, experimental teratology, which is doubtless 

 a branch of pathology, has made most important advances in the 

 knowledge of the laws of normal development, the laws which govern 

 the details of the regular formation of the embryo. Here also no 

 sharp line can be drawn between pathology and embryology. Patho- 

 logy takes its place alongside of embryology, with equal right and 

 equal importance. 



Thus we see pathology placed centrally among the biologic 

 sciences, bound inseparably to all of them, not subordinate to any 

 but their equal, receiving help from all sides but giving as much in 

 return. Lastly, it must be stated that it is the problem of life which 

 forms the subject of pathologic work. Even though it wanders in 

 its own ways, and possesses its especial questions, it is finally led to 

 the general question of every biologic investigation. 



1 Marchand, Eulenburg's Real Encyclopaedie , xv, 432, 1897; Bonnet, Ergebn. 

 d. Anat. u. Entwicklungsgesch. ix, 820, 1899; Wilms, Die Mischgeschwiilste, 1899- 

 1902. 



