Transcriber's note:

The following corrections have been made:

[Title page:] Period added after J in "J B. Lippincott Company"
[Dedication:] Period added after "DAYS IN SERBIA"
[Table of Contents:] "Epidemic, By Dr. Otto Schöbl" By changed to by
[p. 21:] "christendom" changed to Christendom
[p. 32:] Removed italic type from the word genus in "genus Ctenocephalus"
[p. 62:] "secondary to this July case" July changed to June
[p. 78:] "known as Loemopsylla cheopsis" Loemopsylla changed to Lœmopsylla
[p. 132:] "While cases 5, 2, 19 and 24" 2 changed to 11
[p. 139:] "fleas from a plagueinfected house" plagueinfected changed to plague-infected
[p. 142:] "usually met with in" with in changed to within
[p. 147:] "Echinococcus teniæformis was found in the liver" teniæformis changed to taeniæformis
[Index:] "Swellengreble" changed to Swellengrebel
[Footnote 5:] "Jena (1903) 2" added comma after closing bracket