ORGAN IZ 

 KNOWLEDGE 



X IN/ STORY 

 AND' PICTURE 



Vv 



V is the twenty-second letter of the English alphabet. There 

 was no corrosponding letter in the Phoenician alphabet, and in 

 the Greek the letter which resembled v in form was a vowel, u. 

 In Latin the V, as well as the rounded U form, was used, but no 

 distinction was made between them in early times, and even in 

 English, after the v sound had become well established, the two 



letters were used interchangeably. Dictionaries and alphabetically arranged lists of words 

 made no distinction between those beginning with these two letters. Not until the seven- 

 teenth century were the two permanently differentiated. As regards phonetic value, v is 

 closely related to /, and in allied languages the two are often confused. The close connec- 

 tion is shown by the substitution of v for / in the plurals of such words as leaj, leaves; 

 staff, staves. V has always the same sound, and is pronounced with the upper teeth pressed 

 against the lower lip. 



VACATION SCHOOLS. See SCHOOL, sub- 

 head Vacation Schools, page 5241. 



VACCINATION, vak si no' shun, a form of 

 inoculation practiced generally in civilized 

 countries for the prevention of smallpox. It 

 has been the means of vastly diminishing the 

 number of cases of this dread disease, which is 

 now one of the rarest instead of one of the 

 commonest maladies. The principle upon 

 which it is based is that if the individual ac- 

 quires the disease in a mild form, antitoxins 

 for the cure of the ailment will be manufac- 

 tured in his own blood and render him immune 

 to attacks of real smallpox for a number of 

 years. The process consists of rubbing or scrap- 

 ing into the skin (usually on the arm) virus 

 taken from the pustules formed on the abdo- 

 men of a healthy cow, which has been inocu- 

 lated with disease germs. 



The person vaccinated undergoes an attack 

 of cowpox, or vaccinia, which is the cow or 

 horse variety of smallpox. The arm becomes 

 sore and swollen and a vesicle containing a 

 clear fluid forms. A crust then forms over the 

 sore, which, if not pulled off through scratching, 

 will drop off in about two weeks, leaving a scar. 

 In some cases fever, headache and dizziness are 

 accompanying symptoms. There is no danger 

 from this operation, provided the physician 



uses clean instruments, and the proper precau- 

 tions are afterwards taken to avoid infection. 

 The directions of the attending surgeon should 

 be carefully followed. Children who are vac- 

 cinated must be watched to see that they do 

 not scatch the sore, as infection from finger 

 nails is a source of danger. Vaccination came 

 into general favor through the efforts of Dr. 

 Edward Jenner, an English physician. See 

 JENNER, EDWARD. C.B.B. 



Consult Millard's The Vaccination Question. 



VACUUM, vak'uum, a term meaning empti- 

 ness and applied strictly to a space containing 

 nothing. Ordinarily, however, it refers simply 

 to a space where the pressure is appreciably less 

 than that of the atmosphere, as in an engine 

 cylinder. A perfect vacuum has never been ob- 

 tained, for it is impossible to exhaust all the 

 air from a given space, and even were this 

 possible the ether which fills all space would 

 still remain. But very low pressures may be 

 obtained by special air pumps (see AIR PUMP). 

 Sound and heat and even electricity will not 

 traverse a high vacuum, but the brilliant glow 

 of an electric discharge in a moderately high 

 vacuum is made use of in the vacuum-tube 

 lighting system. The most perfect vacuum so 

 far obtained is that over mercury in a barome- 

 ter tube (see BAROMETER). 



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