M 28
satisfactorily explained. We know that plague is a disease of rats communicated to man through the medium of the rat flea but we know little of the reason for the rise and fall in the incidence of the disease among rats or what natural causes have an influence on the virulence of the plague bacillus. In spite of the continuous campaign against them, owing to the rapidity with which they multiply, there still is and probably always will be a sufficiency of rodents in the Colony to light up and maintain an epidemic. The value of a continuous anti-rat campaign lies in the early information it affords of an epizootic.
The cases of Plague recorded in the Colony since the discovery of this disease in 1894 are given in the following Table:
YearCasesYearCases 18945,0001913408 18954419142,146 18961,2041915144 189721191639 18981,320191738 18991,4861918266 19001,0871919464 19011,6511920138 19025721921150 19031,41519221,181 19045101923148 190527219240 190689319250 190724019260 19081,0731927 190913519284 19102519292 191126019300 19121,857Enteric. The number of cases reported was 221 as compared with 207 for the previous year. All the cases were sporadic and as is usual in such the source of infection could not be traced. There is no evidence that any case contracted the disease through the public water supply.
Helminthic Disease. The hospital returns show 31 cases of ankylostomiasis, 3 cases of cestodes and 3 cases of clonorchis and 23 cases of ascaris infection. These figures are of no value in gauging the prevalence of helminthic diseases for they only represent the cases which were treated for worms alone. It is estimated that 75 per cent of adult Chinese harbour ascaris. It is probable that a considerable number have trematodes,