Immunization against Pneumococcus. 



337 



the blood two to five minutes after its introduction into the trachea 

 of animals. Moreover, even such substances which do not easily 

 diffuse through other tissues may sometimes readily pass through 

 the mucosa of the respiratory system. Thus, for instance, Colin 

 introduced intratracheally 10 c.c. of i per cent, solution of curare 

 (which is not absorbed from the intestine) killing the dog in 15 

 minutes. The rate at which fluids may be absorbed from the 

 trachea is remarkable. Colin 2 describes an experiment in which 

 he introduced intratracheally into a tracheotomized horse a con- 

 tinuous stream of warm (30°-35°) water at a rate of six liters per 

 hour for 3^2 hours in succession without causing any noticeable 

 discomfort to the horse. When at the end of the experiment the 

 horse was sacrificed the observer could not detect any water in 

 the trachea or bronchi, all water having been thoroughly absorbed. 



In spite of this remarkable power of absorption, trachea was 

 not generally employed as the route for the parenteral introduc- 

 tion of foreign substances in the experimental work until recently 

 when Besredka 3 called attention to the fact that trachea consti- 

 tutes as good and perhaps even a better site of introduction of 

 antigen into the experimental animals than any other employed. 

 During the summer of 1920 one of us had the privilege of personal 

 acquaintance with the work of Besredka and it is this experience 

 that suggested the possibility of utilizing the tracheal route for 

 the purpose of production of immunity to pneumococcus. This 

 investigation was undertaken with the hope that intratracheal 

 introduction of pneumococcus antigen might be particularly ad- 

 vantageous in view of the fact that it suggested the possibility of 

 increasing the local resistance of the tissues of the respiratory 

 system to pneumococcus in addition to creating the state of hu- 

 moral immunity. The experiments which will be reported later will 

 bear on the question of successful production of increased local 

 tissue-resistance. In this paper we wish to report on the relative 

 value of intratracheal route for parenteral introduction of pneumo- 

 coccus antigen as compared with subcutaneous, intravenous and 

 intrapleural routes and as measured by the concentration of circu- 



1 Colin, Traite de physiologie comparee des animeau, Paris, 1873, t. 88, p. 112. 



2 Colin, loc. cit., pages 1 09-1 10. 



3 Besredka, Ann. Inst. Pasteur, 1920, xxxiv, 51 and 361. 



