 Having proposed a model of globular proteins, Wrinch investigated whether it was consistent with the available structural data.She hypothesized that bovine tuberculin protein (523) was a "C1" closed cyclol consisting of 72 residues and that the digestive enzyme pepsin was a "C2" closed cyclol of 288 residues.These residue-number predictions were difficult to verify, since the methods then available to measure the mass of proteins were inaccurate, such as analytical ultracentrifugation and chemical methods.