Biology and Medicine 447 



One of the most fatal diseases in days gone by was menin- 

 gitis, caused by the bacterium Diplococcus intracellularis, 

 which develops in the meninges or membranes surrounding 

 the brain and spinal cord, setting up an inflammation result- 

 ing in death, or, if the victim is spared, often leaving paraly- 

 sis, imbecility or some other dread condition in its wake. 

 With the discovery of the causative organism some thirty 

 years ago, biology set itself to find a remedy. 



It is a well-known fact that both among men and lower 

 animals there are many instances of natural immunity and 

 susceptibility to disease. The native cattle of Austria- 

 Hungary and Japan are relatively immune to tuberculosis, 

 while other breeds are very susceptible. The Algerian sheep 

 are comparatively immune to anthrax, to which all other 

 sheep are extremely susceptible. Field mice are immune to 

 glanders, while the house mouse is susceptible. The negro 

 is more resistant to yellow fever and susceptible to tubercu- 

 losis than the white race. Malaysians are very susceptible to 

 beriberi, while other races are much less so. 



While some immunity to disease is thus "natural" or in- 

 born, other immunity may be "acquired." After recovery 

 from typhoid fever the subject is unlikely to have a recur- 

 rence of the disease for several years. The victim who has 

 successfully withstood an attack of smallpox is thereafter 

 usually protected against its ravages, while we are all familiar 

 with the measles and whooping cough of childhood, which once 

 experienced, give us comparative protection against further 

 attacks. Modern theories and practice of immunity are of 

 very recent date, and yet methods of immunity have been 

 practised from an early date and by primitive people. The 

 Chinese and other orientals were wont to protect themselves 

 against smallpox by putting the scabs of patients into the 

 nose of persons who had not yet taken the disease. In 1721 

 a similar method was introduced in England by Lady Mary 

 Montague, and was practised there until the discovery of 

 Jenner's method of vaccination. The Moors used to protect 

 their cattle from pleuropneumonia by sticking a knife, which 

 had been previously inserted in the lung of an animal which 

 had died from the disease, under the skin of healthy animals. 

 One of the tribes of central Africa, the Vatuas, are reported 

 to immunize themselves against snake venom. 



The various theories of immunity are too complex to be 

 discussed in detail here, but the brief general statement may 

 be made that immunity depends upon certain chemical sub- 

 stances in the blood which either aid in the destruction of 

 bacteria or counteract the poisons which they produce (or 

 both). The former process occurs in vaccination either with 



