LECTURE XVIII. 



ployed, for since that time it has been known that 

 medullary cancers are not due to the proliferation of 

 nervous matter, but consist of cellular elements of 

 another kind. In fact, the body appears 'to us at the 

 present day, as Reichert was the first to note, to be 

 made up of a more or less continuous mass of connec- 

 tive tissue-like constituents, in which at certain points 

 other things, such as muscles and nerves, are imbedded. 

 Now it is in this more or less connected frame-work, 

 that, according to my investigations, genuine new-forma- 

 tion goes on, and that in accordance with the same law, 

 which regulates embryonic development. 



This law of the correspondence between embryonic 

 and pathological development was, as you know, laid 

 down by Johannes Miiller, who continued the investiga- 

 tions commenced by Schwann. But at that time the 

 contents of an ovum were placed on a level with 

 blastema ; it occurred to no one that the whole process 

 of development in the ovum took place within the limits 

 of a cell, but it was concluded simply, that there was 

 a certain quantity of organizable material in the ovum, 

 which in virtue of a peculiar power innate in it, by 

 means of some organizing force, or as those would 

 have it who regard the matter from a " higher" point 

 of view, impelled by an organizing idea transformed 

 itself into this or that particular shape. But here too 

 the conviction has been gradually acquired, that the 

 matter in question is a cellular substance, and if what 

 has been most rigidly maintained by Remak is correct, 

 namely, that the cleavage of the yolk also is due to a 

 visible division of cells, to the growing in of mem- 

 branous partitions into the interior of the ovum, and 

 their coalescence, we have not here to deal with a free 

 organizing impulse taking place within the yolk, but 

 with progressive acts of division on the part of the 



