the chicken tissues investigated can be divided into two classes , depending on the relative concentration of subfractions 2 and 3 ( a and b ) : class a ( subfraction 2 is smaller than 3 ) includes the brain , liver , skeletal muscle , heart , muscular layer of the stomach , and pancreas , and class b ( subfraction 2 is larger than 3 ) includes the intestinal mucosa , thymus , and testes , as well as the liver , heart , and pancreas from a 21-day embryo .
C0086045
concentration
C0006104
brain