TISSUE RECONSTRUCTION FROM DISSOCIATED CELLS 201 



Figure 3. A later stage of rotation-compounded aggregates, showing com- 

 pact aggregates at the "head" of tlie spiral and continuing aggregation 

 toward the "tail." 



gated and their mutual reactions tested. But the major advantage of 

 this system is that, since it is based on simple experimental parameters, 

 it lends itself to rigorous control. It yields highly consistent, repro- 

 ducible results in a form amenable to quantitative assessment. Indeed, 

 it represents an encouraging initial step toward a more precise study of 

 various aspects of cell interactions. 



Aggregation patterns 



The first striking result obtained with this rotation-mediated aggre- 

 gation procedure was that cells from different tissues, when com- 

 pounded by rotation under identical conditions, varied conspicuously 

 and consistently in their manner of aggregation, each kind of cell popu- 

 lation yielding a characteristic aggregation product. The major features 

 by which these cell-type characteristic aggregates differed represented 

 the aggregation pattern of the cells in testing, typical for the given 

 conditions. These features included the number, size distribution, 

 shape, and internal stmcture of aggregates produced in 24 hours, in a 

 standard culture medium* at 70 rpm. and 38° C. For example, dis- 



* Composition of standard medium: Eagle's Basal Medium ( + 1 per cent 

 glutamine) with 10 per cent unfiltered horse serum, 2 per cent fresh chick embryo 

 extract, and peniciUin-streptomycin ( 50 units per ml. each ) . 



