484 WHOOPING-COUGH 



chief symptoms are produced by toxins resident in the bodies of the 

 bacilli. He made control experiments by injecting other organisms, and 

 also by injecting inert substances into the cerebral tissue. 



The evidence, accordingly, that the influenza bacillus is the 

 cause of the disease rests chiefly on the well-established fact that 

 it is always present in the secretions of the respiratory tract in 

 true cases of influenza, and often in very large numbers. The 

 observed relationships of the organism to lesions in the lungs 

 and elsewhere leave no room for doubt that it is possessed of 

 pathogenic properties, but we cannot yet maintain that its causal 

 relationship to epidemic influenza is absolutely established. 



Methods of Examination. — (a) Microscopic. — A portion of the 

 greenish-yellow purulent material which often occurs in little round 

 masses in the sputum should be selected, and film preparations should 

 be made in the usual way. Films are best stained by Ziehl-Neelsen 

 carbol-fuchsin diluted with ten parts of water, the films being stained 

 for ten minutes at least. In sections of the tissues, such as the lungs, 

 the bacilli are best brought out, according to Pfeifler, by staining with 

 the same solution as above for half an hour. The sections are then 

 placed in alcohol containing a few drops of acetic acid, in which they 

 are dehydrated and slightly decolorised at the same time. They should 

 be allowed to remain till they have a moderately light colour, the time 

 varying according to their appearance. They are then washed in pure 

 alcohol, cleared in xylol, and afterwards mounted in balsam. 



(6) Cultures. — A suitable portion of the greenish-yellow material 

 having been selected from the sputum, it should be washed well in 

 several changes of sterilised water. A portion should then be taken on 

 a platinum needle, and successive strokes made on the surface of blood- 

 agar tubes. The tubes should then be incubated at 37° C. , when the 

 transparent colonies of the influenza bacillus will appear, usually within 

 twenty-four hours. These should give a negative result on inoculation 

 on ordinary agar media. 



Whooping-cough. 



Up to the year 1906, the chief result of bacteriological 

 observations, of which those of Spengler, Krause and Jochmann, 

 and Davis may be mentioned, had been to demonstrate the very 

 frequent presence of minute influenza-like and haemophilic 

 bacilli in the sputum and also in the lesions in this disease. In 

 the year mentioned, however, Bordet and Gengou published 

 an account of another minute organism, and brought forward 

 certain facts which gave strong support to its etiological re- 

 lationship. A short description of this bacillus may accordingly" 

 be given. 



Characters of the Bacillus (Bordet-Gengou). — The organism, 

 as seen, for example, in the sputum, occurs in the form of 



