NATURAL AND ACQUIRED IMMUNITY 115 



Prussian War (1870-71) was due to typhoid fever. During the 

 Spanish- American War, there Avas one case of typhoid to approx- 

 imately every five men. 



Largely through the efforts of Wright in England and Russell in 

 the United States, prophylactic inoculation against typhoid and 

 paratyphoid fever was introduced into the British and United 

 States armies, respectively. It was made compulsory in the United 

 States Army in 1911. It should also be added that excellent san- 

 itary precautions have been introduced and enforced. The in- 

 cidence of typhoid fever among the troops of the United States 

 Army during the World War shows quite definitely the impor- 

 tance of these measures. There was only one case for every 3,756 

 men, which is in marked contrast to one for every five men during 

 the Spanish-American War. 



After the last war, according to Simmons (1941), the triple 

 vaccine (against typhoid and paratyphosus A and B) was replaced 

 first by typhoid-paratyphoid A and later by a typhoid vaccine only. 

 Simmons states that the army has now gone back to the triple vac- 

 cine. He also mentions that pneumococcus polysaccharide solu- 

 tion is giving encouraging results in experimental immunization 

 against pneumonia. 



Immunization With Bacterial Polysaccharides. — The employ- 

 ment by the army, as reported by Simmons, of pneumococcus poly- 

 saccharide is justified by the discovery of Francis and Tillett 

 (1930) that Type I pneumococcus polysaccharide injected into 

 human beings gave rise to mouse protecting antibodies. Accord- 

 ing to Horsfall and Goodner (1936) it has been shown that anti- 

 body response to the injection of Type I polysaccharide can be 

 obtained in man, mouse, horse, cat and dog but not in the rabbit, 

 rat, guinea pig and sheep. Boivin (1935, 1936, 1937) has ap- 

 parently isolated carbohydrate-phosphatide compounds from S. 

 enteritidis and 8. aertrycke which stimulated the formation of 

 specific antibodies in rabbits. Similar antigenic polysaccharide- 

 phosphatide complexes have been isolated by Raistrick and Topley. 

 The latter and his associates (1937) obtained antigenic fractions 

 from E. typhosa which contained a large proportion of poly- 

 saccharide. It should be remembered, however, that not all type 

 specific pneumococcus polysaccharides have been shown to stimulate 



