198 APPLIED BACTERIOLOGY 



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, 

 characterized 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 

 in the years 1729, 1732-33, 1737, 1742, 1758, 1762, 1767, 

 1775, 1782, 1803, 1833, 1837, 1847. A good account of 

 the epidemic of 1847 is to be found in the medical journals 

 of that date by the late Dr. Peacock. Prom 1847 till the 

 December of 1889 England has been free from its ravages. 

 In the May of that year the disease broke out in Asia, 

 spreading to St. Petersburg by October, and reaching 

 London by November, though subsequent 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 popula- 

 tion suffered from the disease. Since the spring of 1890 

 there have been sporadic cases, and a regular epidemic 

 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 

 the respiratory lesion was by far the most common, in 1890-91 

 the gastro-intestinal, and it was not till the third year of the 



