We see that many parts of the body, for example the 

 thorax, at a certain moment of time not only do not 

 exist completely, but also cannot exist at that time. 

 We conclude that it did not exist not because we do 

 not observe it, but because we see in this place, 

 where the thorax must appear, the appearance of true 

 amnion; from here we conclude that the thorax, which 

 is not revealed, cannot exist and as a matter of fact 

 does not exist. 



These arguments of Wolff also concern development of the pelvis 

 and the digestive tract. "I consider," he concluded, "that this 

 is the most important evidence in favor of epigenesis." 



From here it can be concluded that the parts of the 

 body do not always exist, but are formed gradually; 

 during this it is not important by what means formation 

 is accomplished; I do not say that the parts are formed 

 by the accumulation of particles , or by any kind of 

 fermentation, by means of mechanical causes or by 

 powers of soul ; I only say that the parts are truly 

 formed .... Instead of the center of the intestine, 

 i.e. the entire intestinal tract from duodenum to 

 rectum, there are two plates with rolled up anterior 

 edges, and in the rest plates divided are falling 

 behind each other .... I ask, therefore, are these 

 plates the formed intestine? No one, of course, will 

 confirm this . Thus , I conclude that the complete and 

 formed parts do not always exist, but are formed in a 

 determined period after conception. ($ 155) 



This necessarily brief and selective statement of Wolff's ideas 

 gives a clear view of the means of exact investigation of 

 embryonic development by which he finally consolidated and 

 confirmed the truth of epigenetic opinions and the fruitlessness 

 of the preformation idea. 



Wolff was insufficiently evaluated by contemporaries. 

 Forty years later the majority of them had no idea about the 

 existence of his main work. Meckel's merit is not only that 

 by publishing his translation he made Wolff's work general 

 property, but also that he helped restore Wolff's priority 



86 



