Dr. Farr makes the following remarks on the plague, in his report on the cholera of 1848–9: “It is endemic in the Delta of the Nile, and periodically decimates the population of Cairo and Alexandria.... It grows gradually less fatal up the Nile, and is less frequent and destructive in Upper than in Lower Egypt, in the high lands and in the desert, than on the low lands on the shores of the Mediterranean.” Speaking of Cairo, he says: “Through the midst of it passes the Great Canal, into which the sewers are discharged over carrion, excretion, and mud. At the yearly overflow of the Nile, its waters, filling this canal, are distributed over the city, and drunk by its wretched inhabitants.” The plague resembles cholera in being much promoted by crowding and want of personal cleanliness. The natives of Gurhwal, a province in the north-west of British India, in which the plague has been present for the last thirty years, believe that it may be transmitted from one place to another in articles of diet, such as a jar of ghee.[34] [Sidenote: MODE OF PROPAGATION OF YELLOW FEVER.] Yellow fever, which has been clearly proved by Dr. M’William and others to be a communicable disease, resembles cholera and the plague in flourishing best, as a general rule, on low alluvial soil, and also in spreading greatly where there is a want of personal cleanliness. This disease has more than once appeared in ships sailing up the river Plate, before they have had any communication with the shore. The most probable cause of this circumstance is, that the fresh water of this river, taken up from alongside the ship, contained the evacuations of patients with yellow fever in La Plata or other towns. It was long ago observed, that dysentery was apparently propagated by the drinking of water containing excrementitious matters.[35] The frequent appearance of this disease in Millbank prison, when the Thames water was used, is a confirmation of this; and Dr. Bryson has lately related a number of instances where both dysentery and fever seemed to be occasioned by the water of the Yangtse-Kiang, the Canton river, and other rivers of China.[36] What very much confirms this view of the case, is, that nearly all the patients were afflicted with great numbers of intestinal worms (_lumbrici_); for it cannot be supposed that the worms could proceed from malaria, miasmata, or any of the causes which are frequently believed to occasion dysentery and fever. The eggs of the lumbrici were no doubt contained in great numbers in the water of the densely populated Chinese rivers.