DISSOCIATION AND REAGGREGATION OF EMBRYONIC CELLS 227 



Dissociated embryonic cells tended to re-aggregate when their concentration (num- 

 bers) reached a certain minimal level. When organ rudiments of chick and mouse 

 embryos were disassociated together into mixed suspensions, there was ready re- 

 aggregation to form chimeric tissues, often with histotypical differentiation. This 

 occurred even when such divergent types of cells as cartilage, nerve, liver, and 

 melanotic cells were intermixed. When similar (tissue) type cells from mouse and 

 chick were intermixed, the reconstituted mass included cells from both generic 

 origins. When the intermixed cells were from dissimilar tissue origins (i. e. , chick 

 kidney and mouse cartilage) there was a clear-cut separation of the re-aggregates. 

 There was demonstrated, therefore, preferential re-aggregation according to the 

 original identities of the embryonic differentiating cells, rather than to generic or- 

 igin. 



RESULTS: This exercise is perhaps more difficult than the above description suggests. 

 Nevertheless, it is recommended that the student, after he has mastered most of 

 the other procedures of this book, and the basic procedures of tissue culture (isola- 

 tion culture) work, attempt to repeat one or another of Moscona's described exper- 

 iments. The rewards will far out-weigh the effort, and the results will contribute 

 to one's concept of organismic influences in development. (See also - section #26 

 on "Behavior of Isolated Embryonic Cells. ") 



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