THE PNEUMOCOCCUS 323 
septicemia. Encapsulated pneumococci are found in the blood and 
visceral organs, particularly the spleen, which is enlarged, and the 
peritoneal fluid. Rabbits are somewhat less susceptible, and the 
results of inoculation with pneumococcic exudates or cultures depend 
upon the virulence of the organisms, the size of the dose, and the 
method of inoculation. ^ The intravenous or subcutaneous inocula- 
tion of virulent cultures leads to a fatal septicemia, death occurring 
within five days as a rule. The less virulent organisms, which do not 
kill the animal within a few days after inoculation, frequently cause 
localized abscess formation with a fibrinous exudate. The nature and 
extent of the lesions induced depend largely upon the time which 
elapses between inoculation and the death of the animal. In general 
it may be stated that localized lesions appear when less virulent 
organisms are injected. Intravenous injections are more effective 
than subcutaneous inoculations of the same amount of organisms. 
Guinea-pigs are relatively non-susceptible to pneumococcus infection. 
Many attempts have been made to reproduce the typical patho- 
logical lesions of lobar pneumonia in experimental animals. Wads- 
worth- succeeded in reproducing typical lobar pneumonia in rabbits 
by first partially immunizing them to the organism in order to local 
ize the lesions hi the lungs. Lamar and Meltzer,'* and Wollstein and 
Meltzer^ produced lobar pneumonia in dogs by the method of tracheal 
insufflation devised by Meltzer; and Winternitz and Hirschf elder ^ 
have been equally successful in producing lobar pneumonia in rabbits. 
The method consists essentially in forcing suspensions of pneumo- 
cocci deep into the terminal bronchioles and their alveoli. Cole^' has 
shown that the strain of organism influences the results; organisms of 
slight virulence give negative results, and organisms possessing too 
great virulence cause a generalized septicemia with congestion and 
edema of the lungs as the only local pulmonary manifestations. 
Types of Pneumococci. — Kruse and Pansini^ as early as 1891 called 
attention to the dift'erences, both cultural, morphological and in 
virulence, which they observed in studying 84 strains of pneumococci 
isolated from many cases of pneumonia. They believed that there was 
no sharp line of demarcation between the pneumococcus and Strepto- 
coccus pyogenes, because their various strains included all variants 
between the two types of organisms. Rosenow^ reported the transmu- 
tation of typical pneumococci to Streptococcus pyogenes by a series 
of animal passages and cultural manipulations. Cole^ has been unable 
to confirm this observation in any one of several hundred strains. The 
observation of Holman, that streptococci and pneumococci are not 
infrequently found in the tissues and even occasionally in the ])lood of 
guinea-pigs, is of great significance in this connection. 
' Kruse and Pansini: Ztschr. f. Hyg., 1892, 11, 279. 
2 Am. Jour. Med. 8ci., 1904, 127, 851. ' Jour. Exp. Med., 1912, 15, V.V.^. 
* Ibid., 1913, 17, 353, 424. ^ Ibid., 1913, 17, 657. 
6 Arch. Int. Med., 1914, 14, 56. " Loc. cit. 
8 .lour. Am. Med. Assn., 1913, 61, 2007. » Lor. eit. 
