~3. B. Enteritidis Sporogenes.~--Inoculate tubes of litmus milk with similar amounts to those used in the previous searches, omitting tube No. 1 (_vide ante_ 1-3) place in the differential steriliser at 80° C. for ten minutes and then incubate anaerobically at 37° C. for a maximum period of forty-eight hours. Complete the investigation as detailed under the corresponding section of water examination (see page 438). ~4. B. Diphtheriæ.~-- (A) 1. Plant three sets of serial cultivations, twelve tubes in each set, from (a) cream C^{2}, (b) deposit D^{1} upon oblique inspissated blood-serum, and incubate at 37° C. 2. Pick off any suspicious colonies which may have made their appearance twelve hours after incubation, examine microscopically and subcultivate upon blood-serum and place in the incubator; return the original tubes to the incubator. 3. Repeat this after eighteen hours' incubation. 4. From the resulting growths make cover-slip preparations and stain carbolic methylene-blue, Neisser's method, Gram's method. Subcultivate such as appear to be composed of diphtheria bacilli in glucose peptone solution. Note those in which acid production takes place. 5. Inoculate guinea-pigs subcutaneously with one or two cubic centimetres forty-eight-hour-old glucose bouillon cultivation derived from the first subcultivation of each glucose fermenter, and observe the result. 6. If death, apparently from diphtheritic toxæmia, ensues, inoculate two more guinea pigs with a similar quantity of the lethal culture. Reserve one animal as a control and into the other inject 1000 units of antidiphtheritic serum. If the control dies and the treated animal survives, the proof of the identity of the organism isolated with the Klebs-Loeffler bacillus becomes absolute. 7. Inoculate guinea-pigs subcutaneously with filtered glucose bouillon cultivations (toxins?) and observe the result. (B) 1. Emulsify the remainder of the deposit with 5 c.c. sterile bouillon and inoculate two guinea-pigs, thus: guinea-pig a, subcutaneously with 1 c.c. emulsion; guinea-pig b, subcutaneously with 2 c.c. emulsion; and observe the result. 2. If either or both of the inoculated animals succumb, make complete post-mortem examination and endeavour to isolate the pathogenic organisms from the local lesion. Confirm their identity as in A5 and 6 (_vide supra_). ~5. Bacillus Tuberculosis.~-- (A) 1. Inoculate each of three guinea-pigs (previously tested with tuberculin, to prove their freedom from spontaneous tuberculosis) subcutaneously at the inner aspect of the bend of the left knee, with 1 c.c. of the deposit emulsion remaining in one or other tube (D^{1} or D^{2}). 2. Introduce a small quantity of the cream into a subcutaneous pocket prepared at the inner aspect of the bend of the right knee of each of these three animals. Place a sealed dressing on the wound. 3. Observe carefully, and weigh accurately each day.