This disease repeatedly ravaged the then centers of dense population, Central Asia, Mesopotamia and Southern Asia, in the reigns of Tiglath Pileser (1120–00) and Nebuchadnezzar (605–562). The sickness affected the citizens of ancient Babylon; and the described features of the epidemics were such as we have today in those of Influenza, cough, headache, fever, pain in the eyeballs, and copious tears and water gushing from the nose, stained with blood or all blood. The Sanskrit historians gave the name “Plu” to the disease, probably from the flowing nasal discharge. It is an uncanny coincidence, that our Hawaiian people, who are descended from the Indian branch of the Indo-European family of nations, use the softer letter p in pronouncing the shortened form of the word Influenza, Plu for Flu. Unknowingly, the Hawaiians are using probably the word that their ancestors used 2,500 years ago in India on the banks of the river Sindhu or Indus. EXPLANATION OF MEDICAL WORDS. Before entering upon a description of the epidemics of Influenza, which have ravaged the various countries of the world, it is essential to explain the meanings of certain medical words used in connection with epidemic, contagious and infectious diseases. The definitions which are given, if not exactly orthodox, are fairly in accord with modern views, and are clear, simple, and should be easily understood by any ordinary reader. _Infectious._ A disease acquired without any direct contact with a sick person; the infection may be carried by a person in apparent good health, or by any intermediary substance, or by the entrance of a non-immune person into a room, house, or any place of human residence, or occupied as such; where there has been recently any infectious disease, such as Flu, Scarlet Fever, Measles or Small-pox, etc., etc. _Infection._ The entrance into the system or body of living disease producing germs, such as by (a) Droplet infection; bacteria infected minute particles or droplets, ejected by sneezing, coughing, spitting and talking. (b) Aerial dust particles coated with bacteria. (c) Mixed, more than one bacterium or organism present in the system, they may enter together or one precede the other. _Contagious._ A disease acquired from a direct contact with the sick. _Contagion._ The spreading of a disease by direct or indirect contact. (a) Direct contagion. (b) Indirect contagion or mediate, as by a “carrier,” who is apparently in good health, but nevertheless carries disease and can convey it to other non-immune persons. (c) By means of Fomites (hereafter defined). _Contagium._ The virus or poison which transmits disease, such as the vaccine used in anti-smallpox vaccination, which in former years was obtained from the vacca or cow, now the calf is the source of supply.