DRUGS 215 



of 20 to 40 feet with evergreen opposite entire leaves, and tubu- 

 lar rose-colored or yellow flowers in racemes. The tree en- 

 dures temperatures ranging from the hottest which occur in 

 the Tropics to about 35 F. Cinchona apparently prefers a 

 humid climate with a rainfall of 50 to 60 inches. 



In Java it is chiefly C. ledgeriana which is cultivated, while 

 in Ceylon attention has been given mostly to C. succirubra. In 

 recent years, however, the cultivation of cinchona in Ceylon 

 has greatly diminished. Cinchona trees are propagated mostly 

 from seed. The seed is planted in nurseries from which young 

 seedlings are taken after reaching a height of about I foot and 

 planted in the field at a distance of 4 feet apart. Later, during 

 the growth of the trees, they are thinned to a distance of 12 

 by 12 feet. The tree may also be easily propagated by budding 

 or grafting. 



As already indicated, the chief source of quinin at present is 

 found in the two species C. ledgeriana and C. succirubra, par- 

 ticularly the former. It has been found that the percentage 

 of quinin in the bark increases gradually with age up to about 

 4 years. In fact, as a general rule, it is considered that the 

 maximum percentage of quinin is found in bark from trees 

 6 to 9 years old. The yield of bark from cinchona trees varies 

 greatly. In trees 9 to 10 years old an average yield of dried 

 bark is about 22 pounds per tree, of which about 15 pounds 

 is derived from the trunk and smaller quantities from the 

 branches and roots. The percentage of alkaloids in the bark 

 also varies greatly according to species and condition. In 

 wild trees the average quantity of alkaloids in the bark is 

 about 6 to 7 per cent., of which one-half to two-thirds is quinin, 

 at least in the case of C. calisaya, but cinchonidine is the pre- 

 dominating alkaloid in C. succirubra. There are various other 

 alkaloids in the bark of the cinchona trees. 



The United States imports about 3,600,000 pounds of cin- 

 chona bark annually. This bark is obtained, as already indi- 

 cated, from the trunk and roots, but the root bark is considered 



