--------------------+-----------------------------------+-------------- Starch-iodide | BACTERIA ON AGAR PER C.CM. | Reaction After One +-----------------+-----------------+ B. Coli Per Hour. | 1 Day at 37 C. | 2 Days at 20 C. | 100 c.cms. --------------------+-----------------+-----------------+-------------- 000[¤][¤] | 40 | 15 | 0 0000[¤] | 37 | 18 | 8 00000 | 68 | 268 | 34 00000 | 115 | 553 | 61 Raw water | 114 | 685 | 89 --------------------+-----------------+-----------------+-------------- The number of [¤] signs indicates the intensity of the reaction. BIBLIOGRAPHY [1] Nissen. Zeit. f. Hyg., 1890, =8=, 62. [2] Delépine, J. Soc. Chem. Ind., 1911, =29=, 1350. [3] Phelps. Water Supply Paper No. 220, U. S. Geo. Survey. [4] Wesbrook, Whittaker, and Mohler, J. Amer. Public Health Assoc., 1911, =1=, 123. [5] Lederer and Bachmann. Eng. Rec., 1912, =65=, 360. [6] Harrington. J. Amer. Waterworks Assoc., 1914, =1=, 438. [7] Ellms. Eng. Rec., 1911, =63=, 472. [8] Heise. Philippine Jour. Sci., 1917, =12=, A, 17-34. [9] Norton and Hsu, Jour. Inf. Dis., 1916, =18=, 180. [10] Langer. Zeit. f. Hyg., 1916, =81=, 296. [11] Longley. J. Amer. Public Health Assoc., 1915, =5=, 920. [12] Comte. J. Pharm. Chim., 1916, =14=, 261. [13] Massy. J. Pharm. Chim., 1917, =15=, 209. CHAPTER IV BACTERIA SURVIVING CHLORINATION A disinfectant is usually described as a substance capable of destroying bacteria and other micro-organisms, and an antiseptic as one that restrains or retards their growth or reproduction. This distinction is entirely arbitrary as the ability of a substance to kill organisms or merely inhibit their growth depends upon the concentration employed. Chlorine and hypochlorites, even in minute doses, exert a toxic effect that is sufficient to produce death in organisms but when still smaller concentrations are employed the toxic effect is transient and the reproductive faculty may be entirely regained.