EBEN J. CAREY 83 



tube. The right-handed helicoidal reaction of the mesenchyme, 

 therefore, is due to the left-handed helicoidal growth of the epithelial 

 tube. 



1 1 . The normal asymmetry of the abdominal viscera as well as the 

 position of the gut is dependent upon the clockwise reaction of the 

 stretched mesenchymal cell. These cells are stretched by the left- 

 handed helicoidal growth of the epithelial tube. One factor producing 

 situs inversus viscerum could be the reversal of the spiral growth of 

 the epithelial tube resulting in a reaction of the mesenchyme in a 

 direction opposite, namely counterclockwise, to that which occurs 

 normally. 



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