232 APPLIED BACTERIOLOGY 



ceptible with difficulty. Growth on ordinary agar media 

 is slight and uncertain, but it grows better in broth con- 

 taining grape-sugar and glycerine. The organism must be 

 subcultured every eight days at least, on blood agar, or its 

 vitality will be lost. 



Occurrence, Distribution, and Pathogenesis. — The claim of 

 Pfeiffer's bacillus to be recognised as the specific cause of 

 influenza is admitted and confirmed by many observers, the 

 bacillus being found in the blood and sputum in influenza 

 and in no other disease. Influenza is a contagious disease, 

 characterised by a short period of incubation, namely, from 

 twelve to twenty-four hours, and a sudden onset, with 

 rapid rise of temperature, sometimes preceded by a rigor. 

 It is often accompanied by serious complications, and 

 usually followed by extensive and prolonged loss of 

 strength. The disease is reported to have been epidemic 

 in England frequently during the eighteenth and early 

 part of the nineteenth century. From 1847 till 1888 

 England was free from its ravages. In May, 1889, the 

 disease broke out in Asia, spreading to St. Petersburg by 

 October, and reaching London by November, though sub- 

 sequent reports show that there were some isolated cases 

 as early as October. After Christmas the disease spread 

 with such rapidity that it is shown by statistics that one- 

 third of the male population suffered from the disease. 

 Since the spring of 1890 there have been sporadic cases, 

 and slight epidemics have occurred between January and 

 April in the years 1891, 1892, 1893, 1894. 



The disease may occur in a simple or uncomplicated 

 form, or may be accompanied or followed by respiratory 

 or gastro-intestinal lesions or neuroses. The latter may 

 follow even a simple case, and may be accompanied by 

 respiratory lesions ; but no case involving both respiratory 

 and gastro-intestinal lesions has been recorded. In 1889-90 



