PROPHYLACTIC SERUM AND ANAPHYLAXIS.--On one occasion in Manila in 1913, when some 30 persons were given prophylactic doses of serum, intramuscularly, following a particularly dangerous exposure to fleas from rats dead from plague, there occurred a number of cases of "serum sickness" (anaphylaxis). These persons suffered from severe urticarial, arthralgic and nervous symptoms, lasting for several days and a few were obliged to enter a hospital. In one case the symptoms did not entirely abate for a week. It has been stated that newly-prepared serum is particularly apt to produce serum sickness when used for immunizing purposes. This form of protection is brief (1 to 2 weeks) and is best suited for use where there has been special exposure. PLAGUE VACCINES.--Haffkine originally proposed prophylactic immunization, using killed broth cultures of _B. pestis_ (carbolized to ½ per cent.), giving two injections at intervals of 10 days. Statistically it seems to be shown that this prophylactic immunization with dead bacteria reduces the incidence and mortality one-fourth or one-half (approximately). Experimentally, also, it appears that antibodies (agglutinins) are produced by the vaccine (and modifications thereof). Instead of broth cultures, normal salt solution suspensions of killed pest bacilli are usually used in vaccines at present. Castellani[18] has prepared a combined cholera and plague vaccine for use in countries where both diseases coincidentally prevail. It is a mixed vaccine, so prepared that 1 c.c. of the emulsion contains 1000 millions of plague bacilli and 2000 millions of cholera vibrios. The cultures are grown on agar, killed by phenol and suspended in normal salt solution. [18] A. Castellani: Journal of Ceylon Branch of British Medical Association, June, 1914. He finds (1) that inoculation of the vaccine in the lower animals induces a production of protective substances for the plague bacillus and the cholera vibrio; (2) that the inoculation of human beings is harmless (producing less reaction than the Haffkine inoculation); (3) that a small amount of agglutinins, both for plague and cholera, appear in the blood of most inoculated persons (similar to amounts produced by Haffkine's vaccine), a rough index only of the amount of immunity produced. INDEX