The chief attention was given to the study of the autopsy material and we concentrated on the isolation of B. influenzæ. At the same time we did not neglect the other bacteria making up the flora of the bronchi, lungs and pleural cavity in these cases. The various types were isolated and most of them fully identified. _Technique_ Direct smears were made on sterile slides of all material studied and stained by Gram’s method. The counterstain was always alcoholic fuchsin diluted 1-20 in distilled water. Direct cultures were made on a human blood agar plate containing 5 per cent. blood, which was further smeared just before use with defibrinated blood. This latter procedure was later discarded, as it did not appear to assist to any marked extent the growth of B. influenzæ. Blood broth containing a few drops of defibrinated blood and blood agar slants smeared with blood were also used. Heated blood agar (2-3 c.cm. of defibrinated human blood added to 100 c.cm. of ordinary agar at a temperature of from 90 to 100° C., or as the agar comes from the sterilizer) was used in the last nine cases to replace the blood agar slant in the direct cultures and as the medium of choice for transfers of the B. influenzæ. I prefer the ordinary blood agar plate to the heated blood plate because the former gives readings which are very helpful in distinguishing colonies of various types. B. influenzæ appears as clear, tiny, pinpoint, inert colonies. B. xerosis or the pseudodiphtheria group gives more opaque but often rather similar colonies. Gram negative cocci as M. pharyngis siccus have dry, raised, soon becoming wrinkled, inert colonies, varying greatly in size; M. catarrhalis, more moist, inert colonies. The cocci of the streptococcus viridans group appear as very small colonies with greening, or are not infrequently inert, while thin, flattened colonies with central thickening may sometimes be noted. Those of the streptococcus hemolyticus group occur as small, frequently nipple-like colonies with clear, wide zones of hemolysis; pneumococci as moderately small, moist, dewdrop-like colonies with center collapsing early and with greening; streptococcus or pneumococcus mucosus as larger, watery, sticky colonies with greening and frequently an early clearing near the colonies. TABLE I. BACTERIOLOGY OF THIRTY-TWO AUTOPSIES FROM INFLUENZA CASES.