WHOOPING-COUGH. 477 hour or so it separates into a fluid portion and a mass of whitish, opalescent, irregularly formed flakes or frag- ments. These were selected for study, and were trans- planted by means of a platinum-wire hook to the cul- ture-media. Czaplewski and Hensel used a rather better technique than this, and secured purity of the bacteria in the flakes by transferring them to a test-tube contain- ing pepton solution and violently agitating the tube to wash off foreign bacteria. After washing, the flakes were sown upon culture-media. Hydrocele-fluid was found most useful as a culture- fluid, but particles of sputum were planted upon all the culture-media, and attempts to cultivate bacteria from them were conducted both aerobically and anaerobically. In 13 out of the 16 cases the same bacillus (,r) was iso- lated. The organism when stained and examined micro- scopically appeared as a remarkably short and delicate bacillus, shorter and more slender than the diphtheria bacillus, measuring about 0.8-1.7 p in length and about 0.3-0.4/4 in breadth. When stained it appeared some- what granular, and so resembled somewhat the diphtheria bacillus. Old cultures presented similar involution-forms to those seen in old cultures of the diphtheria bacillus. In general the bacillus resembles the organism found by Afanassiewl and others in cover-glass specimens of whooping-cough sputum, but differs in that spores were seen several times. In pure cultures on coagulated hydrocele-fluid the ba- cillus forms a finely granular layer of pearl-white color. On agar-agar the cultures are opaque, pearl-white, and occur as a thin layer. The colonies upon agar-agar are whitish by reflected light, and straw-yellow or deeper olive-green by trans- mitted light. They are of an irregularly rounded shape and are granular. In gelatin puncture-cultures the growth resembles that of the streptococcus, forming along the track of the wire 1 St. Petersburger med. Wock., 1887, Nos. 39-42.