PNEUMONIA. 351 tion as to allow of frequent relapses ; and it is well known that many cases show a subsequent predisposition to fresh attacks of the disease. This brevity of immunity lessens the probability that in the future we shall dis- cover an antitoxin that shall be powerful in its influ- ence upon the course and termination of the disease. The experiments of G. and P. Klemperer, a few years ago, showed that the serum of immunized rabbits pro- tected animals inoculated with the pneumococcus. The principle failed, however, when applied to human medi- cine. The treatment of pneumonia by the injection of blood-serum from convalescents has also been abandoned as useless and dangerous. Washbourn has recently prepared an antipneumococcic serum which is efficacious in protecting rabbits against ten times the fatal dose of live pneumococci. In general, the lines upon which he operated were those of Behring, Marmorek's work with the streptococcus furnishing most of the details. A pony was subjected to immunization for a period of five .months, allowed to rest three or four months until the live pneumococci introduced were all destroyed, and then bled. Two cases of human pneu- monia seem to have received some benefit from the injec- tion of large doses of this serum. The pneumococcus causes other lesions than croupous pneumonia; thus, Foa, Bordoni-Uffreduzzi, and others have found it in cerebrospinal meningitis; Frankel, in pleuritis; Weichselbaum, in peritonitis; Banti, in peri- carditis; numerous observers have found it in acute ab- scesses; Gabbi has isolated it from a case of suppurative tonsillitis; Axenfeld has observed an epidemic of con- junctivitis caused by it; and Zaufal, Levy, and Schrader and Netter have been able to demonstrate its presence in the pus of otitis media. It has also been reported as oc- curring in the joints in arthritis following pneumonia. The pneumococcus is often present in the mouths of healthy persons. The conditions under which it enters the lung to produce pneumonia are not known.