Hacking cough regarded as true pathognomonic phenomenon of the en trance into the body of the toxic agent of whooping-cough. The longer the period of incubation (i.e., the greater the resistance of the system), the greater the infection and the severer and more prolonged will be the sickness; while the shorter the incubation, the milder the disease and the more brief the period of its duration. Illoway (Pediatrics, Jan. 15, '99).
There seems to be good ground for the opinion that an increased percentage of lymphocytes, at least equaling or ex ceeding that of the poly morph °nue] ear neutrophilie cells, is a Valuable diagnos tic aid before the characteristic symp toms of the disease make the diagnosis easy. But like the doctrine of poly morphounclear leucocytosis in genera], the figures are more convincing in the mass than when considered individually. Alfred Wanstall (Amer. Medicine, Jan. 10, 1903).
Etiology.—The clinical history of the disease points strongly to the existence of a specific organism to which the ca tarrhal and nervous symptoms may be more or less directly attributed; but, so far, pathologists have not determined with certainty the exact micro-organism. Afanassiew in 1887 announced that he had found a characteristic bacillus in the sputum of children suffering from this disease. This discovery was confirmed by a few observers, and for a time his bacil lus was regarded as the exciting organ ism; since then, however, doubt has been thrown upon his conclusions. In 1896 Kurloff described a ciliated protozoon of variable size which he considered to be the specific organism. A year later Kop lik described a slender bacillus somewhat resembling the bacillus of influenza. In December of the same year Czaplewski and Hensel described a short bacterium, somewhat resembling a diplococcus, which they regarded as the same organ ism described by but they are not certain as to its _identity with that of Afanassiew. Still later, Behla comes to the same conclusion as Kurloff, that the specific micro-organism belongs to the protozoa, and is not of a bacterial nature.
This it appears that several micro-or ganisms have been found with sufficient frequency in the sputum of children suf fering from pertussis to be regarded as the exciting cause, but at the present no one germ is universally recognized as such. The contagium off from
the respiratory tract, chiefly in the spu tum; the disease appears to be readily communicated through the air even for a considerable distance, and appears to be specially contagious during the early ca tarrhal stage.
When the sputum is examined during the convulsive stage there is found constantly present a very minute bac terium. It is seen sometimes in the epi thelial cells. It grows on most of the ordinary media; best, however, in hydro cele fluid. It is both anaerobic and aerobic. It is a minute, thin, short ba cillus; it stains with tne ordinary ani line dyes; and is not decolorized by Gram's method. It is somewhat toxic to white mice, but produces no symptoms of whooping-cough in them. Koplik (Johns Hopkins Hosp. Bull., Apr., 'OS).
Bacillus constantly found in the spu tum of 25 children suffering from per tussis. It is a short oval rod, one and one-half to two times as long as it is broad, and the centre stains imperfectly. Generally it is present in large numbers. A thorough washing of the particles of mucus is essential before attempts are made at cultivation. Best medium is a glycerin-agar made with anasarcous fluid. Colonies are moderately small, round, slightly raised, gray or grayish white, and finely granular. Growth is less marked on ordinary glycerin-agar or on agar or glucose-agar, and it does not grow better on blood-serum-agar than on glycerin-agar. In broth cultures there is no turbidity after twenty-four hours, but a sediment sinks to the bot tom of the tube. There is no film on the surface. Gelatin is not liquefied. The microbe is non-motile, forms no spores, and is but slightly resistant to high temperatures. It is a facultative anae robe, and is mostly decolorized by Gram's method. Grape-sugar is not fer mented, nor milk coagulated by it. It does not give a serum-reaction. Experi ments on animals were negative.
In two cases diagnosis was made by examination when there was clinical un certainty. Czaplewsky examined speci mens, and agreed that the microbe was exactly the same as that found by him. Thus, Czaplewsky and Hensel's obser vations are indepencontly confirmed. Zusch (111finch. med. Woch., June 7, '98).