vicissitudes of the people--all this is something more than curious. Unfortunately for the historian of diseases, he has to look for the realities amidst the “favourite opinions” or the “preconceived fancies” of contemporary medical writers. Statements which at first sight appear to be observations of matters of fact are found to be merely the necessary truths or verbal constructions of some doctrine. One great doctrine of the 17th and 18th centuries was that of obstructions: in this doctrine, as applied to fevers, obstructions of the mesentery were made of central importance; the obstructions of the mesentery extended to its lymphatic glands; so that we come at length, in a mere theoretical inference, to something not unlike the real morbid anatomy of enteric fever. Another great doctrine of the time, specially applied by Willis to fevers, was that of fermentations and acrimonies. “This ferment,” says a Lyons disciple of Willis in 1682, “has its seat in the glandules of the velvet coat of the stomach and intestines described by Monsieur Payer[2].” But the Lyons physician is writing all the while of the fevers that have always been common in the Dombes and Bresse, namely intermittents; the tertian, double tertian, quotidian, quartan, or double quartan paroxysm arises, he says, from the coagulation of the humours by the ferment which has its seat in the glandules described by M. Payer, even as acids cause a coagulation in milk, the paroxysm of ague continuing, “until this sharp chyle be dissipated and driven out by the sweat or insensible perspiration.” The lymphatic follicles of the intestine known by the name of Payer, or Peyer, were then the latest anatomical and physiological novelty, and were chosen, on theoretical grounds, as the seat of fermentation or febrile action in agues. On the ground of actual observation they were found about a century and a half after to be the seat of morbid action in typhoid fever.