CHAPTER XVIII. 



INFLUENZA, PLAGUE, RELAPSING FEVER, 

 MALTA FEVER, YELLOW FEVER. 



INFLUENZA. 



THE first accounts of the organism now known as the influenza 

 bacillus were published simultaneously by Pfeiffer, Kitasato, and 

 Canon, in January 1892. The two first-mentioned observers 



found it in the bronchial 



- \r*J ' '*?. sputum, and obtained pure 



. * / ;J *. i cultures, and Canon ob- 



j* . % ' K v f - vv f^ served it in the blood in a 



*'A x few cases of the disease. 



fc * tf, ' fcf&s* " % t It is, however, to Pfeiffer 's 



>;t ' , , work that we owe most of 



i jfv **/{' * 1 *..^> our knowledge regarding 



- ' s ? v '^ | its characters and action. 



*~" /,*?' S-i s results have been 



' c * % / amply confirmed by those 



r of others in various epi- 



fri? ' f '^\*. .'. V / demies of the disease, and 



V ^ , , this organism has been 



. generally accepted as the 



cause of the disease, al- 



FIG. 142. -Influenza bacilli from a culture ^ugh absolute proof is 



on blood agar. j.-n 



Stained with carbol-fuchsin. x 1000. stl11 wanting. 



Microscopical Char- 

 acters. The influenza bacilli as seen in the sputum are very 

 minute rods not exceeding 1 '5 /A in length and '3 p in thickness. 

 They are straight, with rounded ends, and sometimes stain more 

 deeply at the extremities (Fig. 142). The bacilli occur singly 

 or form clumps by their aggregation, but do not grow into chains. 

 They show no capsule. They take up the basic aniline stains 



420 



