  The combinatorics of the BPHZ subtraction scheme for a class of ladder graphs
for the three point vertex in $\phi^3$ theory is transcribed into certain
connectivity relations for marked chord diagrams (knots with transversal
intersections). The resolution of the singular crossings using the equivalence
relations in these examples provides confirmation of a proposed fundamental
relationship between knot theory and renormalization in perturbative quantum
field theory.
