Geome W. Bartelmez 



The renewal of interest in descriptive embryology was one aspect of the 

 reaction to the theoretical argumentation so characteristic of the eighteenth 

 century. By the beginning of the nineteenth century Wolff, Joim Hunter, 

 Tredern, Pander, E. Geoffroy Saint-Hilaire, and Dutrochet had already re- 

 turned to the detailed study of the bird's egg, and in 1819 Dutrochet published 

 his investigation'" on the oviducal history of the hen's egg. Purkinje was the 

 first to see the need of tracking the cicatricula from laid eggs back to ovarian 

 stages. He naturally interpreted the vesicle which he found in the ovarian 

 oocyte at the center of the blastodisc as the female germ itself, "for it appeared 

 to be the first structure in the egg that is 'stimulated to germinate.' " His proof 

 that the supposed hole in the theca folliculi, the porus pellucidus, is in reality 

 a crystal clear vesicle, involved the isolation for the first time of what we 

 now call a nucleus and the first demonstration of a nuclear membrane. More 

 important was the stimulus it gave to others, especially those who had com- 

 pound microscopes, to look for similar structures in other eggs and eventually 

 in other cells. By 1827 von Baer had identified the "vesicula Purkinjii," as he 

 called it, in all the vertebrate and invertebrate eggs he could obtain, including 

 the early ovarian eggs of mammals (see translator's note i). In 1833 Coste" 

 demonstrated it in full-grown eggs of the rabbit. By 1836 Wagner'- had de- 

 scribed the nucleolus ("germinal spot") in many eggs and proclaimed it the 

 prime mover in development. All this obviously played an important role in 

 the development of the cell theory (see Studnicka^). 



The demonstration of the germinal vesicle is the only discovery ordinarily 

 credited to Purkinje's monograph. Another outstanding contribution was 

 the observation that the vesicle disappears at the time of ovulation and that 

 its contents mix with the substance of the "cumulus," as he termed the sur- 

 rounding thickened part of the blastodisc. O. Hertwig," who seems to have 

 been the last embryologist to read Purkinje's monograph, credits him with this 

 discovery. Hertwig apparently knew only the 1830 edition for he errs in say- 

 ing that Purkinje found that the germinal vesicle had already disappeared 

 before the egg had left the ovary (see translator's note 5). 



There are various other important discoveries in the Symbolae which have 

 been neglected or totally forgotten. Purkinje described the change in the 

 nucleo-cytoplasmic ratio as the ovarian oocyte grows. He pointed out that the 

 egg passes down the oviduct with the pointed end foremost and that it may be- 

 come reversed at the time of laying so that the blunt end is often extruded first. 

 He found that the yolk has one axis longer than any other and that the cica- 

 tricula of large ovarian oocytes may occupy various positions with reference to 

 the stigma and petiole. Actually it can rotate freely in the plane of the polar 

 axis (Bartelmez''). Purkinje was the first to note the increase in peritoneal fluid 

 at the time of ovulation, the appearance of the perivitelline space and the 

 change in the consistency of the yolk during the oviducal journey. He named 

 the latebra and gave the first adequate description of its form, its development, 

 and its relation to the cicatricula. 



