CHAPTER XIX. 



INFLUENZA, PLAGUE, RELAPSING FEVER, MALTA FEVER, 

 YELLOW FEVER. 



Influenza. 



The first account of the organism now known as the influenza 

 bacillus was published simultaneously by Pfeiffer, Kitasato, and 

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

 found it in the bronchial sputum, and obtained pure cultures, 

 and Canon observed it in the blood in a few cases of the disease. 

 It is, however, to Pfeiffer's work that we owe most of our 



knowledge regarding its char- 

 !•'•_/ ' . .« , acters and action. His results 



have been amply confirmed by 

 those of others in various epi- 

 demics of the disease, and this 

 ^J''"' _^. ' '' V organism is now generally ac- 

 ' ' ' ~ cepted as the cause of the 



ii^-- 



■ ( , 



i ■ ' /■ ' ^-^ * '' l_ .. • - -•* ' ' ,- disease, although the absolute 



\' ' -I ■ , ->'. , ; '-^ ^r proof, which would be supplied 



'* ; _ ^ ,» -■'"'"'''".; by the production of the dis- 



"y • ( ' ' ^ ■ . ^ • ease by pure cultures, is still 



. ' ^ ^ , . , ' . wantmg. 



'^ ■ '' " Microscopical Characters. — 



Fig. 146. — Influenza bacilli from a cui- fi^g influenza bacilH as Seen 



ture on blood agar. 



Stained with carboi-fuchsin. X looo. m the sputum are very mmute 



rods not exceeding 1.5 /ti in 

 length and .3 ju. in thickness. They are straight, with rounded 

 ends, and sometimes stain more deeply at the extremities (Fig. 

 146). The bacilli occur singly or form clumps by their aggre- 

 gation, but do not grow into chains. They show no capsule. 

 They take up the basic aniline stains somewhat feebly, and are 

 best stained by a weak solution ( i in 10) of carboi-fuchsin applied 



430 



