The transmission of whooping-cough from an infected to a healthy individual naturally led to the assumption that the pathogenic virus was to be looked for in the sputum and the mechanism of the process in the infection by aspiration of little drops of infectious expectorated matter. There are two possibilities to consider: whooping-cough may be regarded either as a local infectious disease of the respiratory tract, the irritant being produced in the larynx or trachea, and (contrary to most other infectious local diseases) by reaction of their toxic products established a permanent immunity in those who had once been affected; or it may be considered as a general infectious disease which, starting primarily from the mucous membrane of the respiratory tract, produces the clinical symptoms through toxic products. As already stated, a number of weighty facts speak for its acceptance as a general infectious disease.
The exciting factors of whooping-cough have been searched for throughout many decades, since Unmet's, and the results obtained time and again, seemingly successful, have brought forward organisms of the greatest biological variety. Deichler, Kurloff, and Behla thought proto zoa were the cause of pertussis, while Moncorvo and Silva-Aranja, Broadbent, Haushalter, Mircoli, Ritter, and others regarded cocci as the pathogenic factors; Burger, Afanassiew, Szemetsehenko, Wendt, and Genser considered bacilli as the causative agents. Quite recently Cza plewski and Hensel on one hand, Jochmann and Krause on the other, and finally Manicatide have described certain bacilli which may bring us nearer to a bacteriological knowledge of whooping-cough.
Czaplewski and Hensel found in the expectorations, after staining with carbol-glycerin-fuchsin and treating the preparations with 1 per cent. acetic acid, many small short bacilli with rounded corners, about the size of an influenza bacillus, but differing from the latter in that they grow on ordinary culture media. The bacilli are two to three times as long as broad. If delicately prepared, polar staining is shown; while if strongly stained, total staining is accomplished. Experiments on animals proved negative, but their regular occurrence, according to the authors, is suggestive of specificity. Cavasse, Wagner, von Zusch, Koplik„ Arnheim, and Iteyher were able on the whole, to confirm the findings (see Fig. 10S).
Jochmann and Krause, in their investigations made at the Ham burg-Eppendorf hospital, found in whooping-cough sputa in a majority of cases tiny, influenza-like bacilli of morphological identity. However, these they say, do not belong to one species, but represent three different ones distinguished from each other biologically, for example by their behavior towards Grain's method of staining. The influenza-like bacillus
found by Czaplewski and Hensel was detected by Jochmann and Krause in only four cases. The latter claim as the cause of whooping-cough an influenza like Gram-negative bacillus (Bacillus pertussis Eppendorf), growing only on culture media containing haemoglobin. They found this organism in eighteen cases.
A third type of bacillus resembling those of influenza, growing in all ordinary culture media and being Gram-positive (bacillus z), was found by Alanicatide. Its specificity he claims to have established by sero therapeutic experiments, immunizing three sheep and two horses and, by injection of the scrum, effecting a cure or at least an in positive whooping-cough cases.
The bacteriological investigations carried on during the last few years have shed much light on the bacteriology of whooping-cough, an oval short bacillus resembling the influenza bacillus being generally re garded as the specific pathogenic factor. The biological details are still matters of contention, but control experiments (made by Reyher) are strongly suggestive of the specificity of Czaplewski's polarbacterium.
Concerning the period of incubation of whooping-cough hardly any thing positive is known. According to the experience of most observers it varies between three and fifteen days. If three weeks after exposure to infection the disease does not develop, the child in question may be regarded as not infected.
With regard to the contagiousness of whooping-cough in the various stages of the process we find, especially among French investigators, divergent statements. Extensive observations and the importance of greater prophylactic safety make it more advisable to regard whoop ing-cough as contagious during its whole course—that is, to keep a child suffering from whooping-cough isolated from healthy children so long as there is cough with expectoration. Recovery from whooping-cough almost always insures immunity for the remainder of life, according to an overwhelming array of observations. Analogous to those infectious diseases which have been etiologically more definitely investigated, this fact of immunity in whooping-cough may likewise be accounted for by reaction products evolved by specific bacterial metabolism. Against such purely theoretic considerations speaks the great uncertainty of our present etiologic investigation, in that children nourished from their mother's breast, even during their infancy, are not uncommonly affected, when we might expect a certain lessened susceptibility of the infant on account of the transference through the mother's milk of such antitoxin from the actively immune mother, who has had the disease.