42 STUDIES ON PATHOLOGIC OVA. 



head upon the chest noticed in some of them. Since these three types of early 

 embryos seem to recur, His emphasized that it was very probable that normal 

 development can be disarranged easily at certain definite stages in prenatal life, 

 a surmise confirmed by contemporary experimental embryology. In the opinion 

 of His, this faulty development almost invariably led to abortion at the end of 

 the second or the beginning of the third month, which period had been noted by 

 A. Hegar (1863) as the time of most frequent abortion of early specimens. It is 

 striking, indeed, that not a single abortus from the later months of pregnancy, 

 which His regarded as capable of continued growth, ever came to his attention. 



Giacomini (1888, 1893) also described several nodular atrophic embryos and 

 very significantly stated that he never met with nodular or atrophic forms in 

 rabbits. In these animals he found only advanced deformities, and these he re- 

 garded as often merely being the result of death of the fetus with subsequent 

 retention. Hence he did not consider them at all comparable to those found in 

 man. Giacomini also stated that he could experimentally produce all forms of 

 nodular and cylindrical embryos in rabbits, and believed that the atrophic forms 

 were due to changes after death, although he preferred not to emphasize this 

 opinion. 



Later, when Giacomini studied these anomalous forms microscopically, he 

 concluded that a classification based on gross appearance only really tells nothing 

 about the nature of the process which has inhibited development, of the time when 

 the changes began, or of their localization and distribution. Hence he emphasized 

 the necessity of a microscopic examination for purposes of scientific classification. 

 He further stated that both the flexed (or kinked) and the cylindrical forms of 

 His could be classed under the atrophic and declared that abortuses can be placed 

 into two main groups, those with and those without an embryo. In 1895 Gia- 

 comini further suggested two subdivisions under each of these groups. He divided 

 those without an embryo into (1) specimens with only the embryo missing, and 

 (2) those with little else than the chorion present. Since Giacomini believed that 

 the embryo and even the amnion can migrate from the chorionic vesicle and the 

 hole through which they pass close again by healing, he further differentiated 

 specimens in which the embryo had migrated out entirely, those in which it had 

 reached the coelom externum, those in which the embryo and amnion had mi- 

 grated from the chorion, and finally, those in which the active migration of the 

 embryo and amnion had everted the chorion. Since the idea of an active migra- 

 tion of the embryo, not to mention that of some of the adnexa, from out the 

 chorion, does not hold, these four types of empty chorionic vesicles require no 

 further consideration. Specimens in which embryos were present Giacomini 

 classed as nodular and atrophic, after His, the latter class including both the 

 cylindrical and the flexed forms of His. Giacomini's great merit lay in recog- 

 nizing a group of specimens without an embryo, in making a careful microscopic 

 study, and especially in undertaking experimental work in order to elucidate some 

 of the problems which presented themselves to him in a study of abortuses. These 

 aspects of his work will be referred to again in later chapters. 



