4. Remove 0.1 c.c. of the emulsion in the first capsule by means of a sterile graduated pipette and transfer it to the second capsule and mix thoroughly. Drop the infected pipette into a jar of lysol solution. This makes up the bulk of the fluid in the second capsule to 10 c.c., and therefore every cubic centimetre of bouillon in capsule II contains 0.001 loop. 5. Similarly, 0.1 c.c. of the mixture is transferred from capsule II to capsule III (1 c.c. of bouillon in capsule III contains 0.00001 loop), and then from capsule III to capsule IV (1 c.c. of bouillon in capsule IV contains 0.0000001 loop). The dilutions thus prepared may be summarised in a table; Capsule I = 1 loopful + 10 c.c. water [.'.] 1 c.c.=0.1 loop. Capsule II = 0.1 c.c. capsule I + 9.9 c.c. water [.'.] 1 c.c.=0.001 loop. Capsule III = 0.1 c.c. capsule II + 9.9 c.c. water [.'.] 1 c.c.=0.00001 loop. Capsule IV = 0.1 c.c. capsule III + 9.9 c.c. water [.'.] 1 c.c. = 0.0000001 loop. 6. With sterile graduated pipettes remove the necessary quantity of bouillon corresponding to the various divisors of ten of the loop from the respective capsules, and transfer each "dose" to a separate sterile capsule and label; and to such doses as are small in bulk, add the necessary quantity of sterile bouillon to make up to 1 c.c. 7. Multiples of the loop are prepared by emulsifying 1, 2, 5, or 10 loops each with 1 c.c. sterile bouillon in separate sterile capsules. 8. Inoculate a series of animals with these measured doses, filling the syringe first from that capsule containing the smallest dose, then from the capsule containing the next smallest, and so on. If care is taken, it will not be found necessary to sterilise the syringe during the series of inoculations. 9. Plant tubes of gelatine or agar, liquefied by heat, from each of the higher dilutions, say from 0.0000001 loop to 0.01 loop; pour plates and incubate. When growth is visible enumerate the number of organisms present in each, average up and calculate the number of bacteria present in one loopful of the inoculum. 10. The smallest dose which causes the infection and death of the inoculated animal is noted as the minimal lethal dose. _Toxins._-- Prepare flask cultivations of the organism under observation in glucose formate broth, and incubate for fourteen days under optimum conditions. (a) Intracellular or Insoluble Toxins: 1. Heat the fluid culture in a water-bath at 60° C. for thirty minutes. (The resulting sterile, turbid fluid is often spoken of as "killed" culture,) 2. Inoculate a tube of sterile bouillon with a similar quantity, and incubate under optimum conditions. This "control" then serves to demonstrate the freedom of the toxin from living bacteria. [Illustration: FIG. 160.--Apparatus arrange for toxin filtration.] 3. Inject intraveneously that amount of the cultivation corresponding to 1 per cent. of the body-weight of the selected animal, usually one of the small rodents.