628 MAN AS A CONQUEROR 



ciple in this type of immunity is the same in all of these cases. 

 Certain cells of the body are roused or activated to form anti- 

 bodies. Thus the invading organisms are destroyed and their toxins 

 neutralized. In other words, the body is active and does its own 

 work by means of lysins, precipitins, agglutinins, and other defense 

 mechanisms. 



Some Examples of Diseases Where Active Immunity Is 



Practiced 



Smallpox is a very ancient disease, having been known for thousands 

 of years. Always epidemic, in the eighteenth century it is said to 

 have caused 60,000,000 deaths in Europe. The disease was brought 

 to America by the Spanish early in the sixteenth century, and three 

 and a half millions of Mexicans died as a result. The American 

 Indians were almost wiped out by epidemics of smallpox that began 

 in early Colonial days. 



The famous discovery of vaccination for smallpox by Edward 

 Jenner was a matter of evolution. The Chinese and Turks used a 

 form of inoculation against smallpox. Lady Mary Wortley Montagu, 

 a famous beauty of her time, and wife of the English minister to 

 Turkey, believed so much in the inoculation practiced by the Turks 

 that she had her own boy inoculated and introduced the practice into 

 England in 1721, a date considerably earlier than that of Jenner's 

 experiments with inoculation. For nearly twenty years, Jenner 

 made observations and experiments, until in May, 1796, he vaccinated 

 a boy of eight with lymph taken from cowpox pustules on the hand 

 of a milkmaid. Shortly after this the boy was inoculated with some 

 pustules of smallpox and failed to take the disease. This discovery 

 resulted in making possible the conquest of smallpox. The present 

 method of preparing vaccine virus is painstakingly safeguarded. 

 Healthy calves, preferably from six months to two years old, are kept 

 under sanitary conditions until it is certain that they have no disease. 

 They are then inoculated with smallpox virus on carefully steri- 

 lized areas on the ventral side of the body. Later these areas be- 

 come covered with small vesicles which contain the smallpox virus. 

 This virus is then collected, placed in sterile containers, treated with 

 glycerol and distilled water, and allowed to stand three to four 

 weeks. It is then ground up and put into small containers for use 

 by physicians. Every step in the process is carefully protected, 

 so that if fresh virus is used there is absolutely no danger to the 



