10 PEEFACE. 



over, since all these, as well as the specimens of group 7, are macerated, and since 

 all manner of gradations are found between the macerated swollen and the macer- 

 ated wrinkled (fetus compressus) specimen, it may be preferable to restrict this 

 term to its original usage. Much would also seem to be gained by an abandonment 

 of such terms as decidua vera and serotina, which, although historical, convey false 

 suggestions. The occurrence of a psuedo decidua does not seem to be at all estab- 

 lished, and the sense in which the term vera was first used necessarily has been lost 

 in the progress of modern embryology. The same thing applies to the term sero- 

 tina. Hence, as suggested by others, it would seem preferable to speak of a parietal, 

 a basal, and a capsular decidua, and finally relinquish the older terms. 



In order to avoid possible confusion through the introduction of new terms, 

 I have added the following diagram, which presents their relationship at a glance: 



Abortus. 



Conceptus. Blood-clot. 

 . Decidua. 



Pus, etc. 



or 



Secundines placenta and membranes. 



Yolk-sac. 



Cord. 



Liquor annul. 



Chorionic vesicle. 

 Amniotic vesicle. 

 Umbilical vesicle. 

 Amniotic fluid magma. 

 Periamniotic fluid. 

 Umbilical cord. 



fEmbryonic disk. 

 Cyema ... .\ Embryo. 



(Fetus. 



In spite of the fact that some great names have long been associated with the 

 rising subject of the pathology of human development, a routine examination of 

 abortuses seems quite worthless to many investigators. This is natural, for, aside 

 from the poor preservation of many of these abortuses, the conditions under which 

 nature performs her experiments on man necessarily are uncontrolled and often 

 also unknown. But there would seem to be no reason for rejecting any testimony 

 which such experiments may offer, though the search be a long and a disappointing 

 one and the conditions not standard. To regard all attempts at a study of these 

 specimens as futile is very largely to abandon man to a cruel fate. He never can 

 be made the subject of accurately controlled experiment or a wholly satisfying 

 study. The rigid requirements of scientific investigation must, in the nature of 

 things, almost always remain unfulfilled. Comparative anatomy, medicine, and 

 pathology, as well as experiments upon animals, undoubtedly offer greater returns 

 merely because the subject of experiment can be bred, nurtured, and sacrificed at 

 the will and by the hand of man. But if it be conceded that in the last analysis 

 the aim of all human effort must be directed toward the amelioration of the lot of 

 mankind, then it would be folly to reject even the chance stalk that may spring 

 from the grain of wheat which lay hidden in a bushel of chaff. 



The conception, as well as the general plan, of this volume is that of Professor 

 Mall himself. It was my happy experience to be invited to share in both. An 

 unkind fate made it impossible for Professor Mall to complete his own work; for 

 his part everyone will feel deeply grateful; for the part that might have been his, 

 others than myself will feel an immeasurable regret. 



