Cattle fed on the refuse from potato-starch factories develop a most obstinate and widespread eczema, beginning on the legs.
"Special Report on Diseases of Cattle" by U.S. Department of Agriculture
It is well known that Feynman diagrams exhibit factorial growth in external legs and also in loops.
Methods for the Reduction of Three-Loop QCD Form Factors
The bottleneck in NLO calculations for a 2 → n process is the 2 + n-leg loop calculation, whose complexity scales factorially with the number of legs in Feynman-diagrammatic methods.
Moriond 2009, QCD and High Energy Interactions: Theory Summary