322 THE STREPTOCOCCUS-PNEUMOCOCCUS GROUP 
also caused by the organism. Indeed, in children the pneumococcus 
is rather more commonly isolated from suppurative processes than any 
other microbe; in adults the incidence of pneumococci in suppurations 
is on the whole considerably less. Middle ear involvement, inflamed 
mastoids, endo- and pericarditis are all frequently caused by the 
pneumococcus. The channel of infection appears to be through the 
blood stream, and pneumococci have been isolated from the blood 
stream in a very large percentage of all cases of lobar pneumonia.^ 
Less commonly the organisms become localized in joints, causing 
arthritis, and around the shafts of bones, causing osteomyelitis. 
Conjunctival inflammation- of varying degrees of severity which 
occasionally leads to ulcer formation is frequently a pneumococcus 
infection. 
It was formerly stated that virulent pneumococci could be obtained 
from the sputinn of fully 30 per cent of normal individuals. The 
supposition was that the patient became the victim of his own organ- 
isms. Extensive studies by Dochez and Avery'' suggest strongly 
that the pneumococci found in the sputum during pneumonia are 
commonly replaced by pneumococci of a less virulent type soon after 
convalescence. Their observations, furthermore, make it justifiable 
to consider those patients who harbor the more virulent types after 
recovery as carriers, precisely as typhoid carriers harbor typhoid 
bacilli after recoAery from typhoid fever. 
Incidence of Carrier Condition in Healthy Contacts with Cases of Lobar 
Pneumonia. •* 
Type of Number of No. positive contacts, 
pneumocorcus contacts 
in patient. examined. Cases. Per cent. 
I 160 21 13.1 
II 149 18 12.1 
Incidence of Pneumococci in Healthy Individuals not in Contact with Cases 
of Lobar Pneumonia. 
Incidence. 
Type of Number of 
pneumococcus. cases examined. Cases. Per cent. 
II j ^' 0.00 
MoreF has found pneumococci in the urine in a considerable number 
of cases even before pulmonary invohement can be detected. 
Animal. —Mice are the most susceptible of laboratory animals to 
infection with the pneumococcus. Small amounts of pneumonic spu- 
tum, exudate or pus injected subcutaneously lead to a rapidly fatal 
' Rosenow: Loc. cit. 
- Axenfeld: Kolle and Wassermann Handb. d. path. Mikroorganismen, 2d ed., 
vol. 6, p. 572. 
^ Quoted by Cole: New York Med. Jour., January 2 and 9, 1915. 
^ Avery, Chickering, Cole and Dochez: Monograiih 7, Rockefeller Institute, October 
16. 1917. 
s Presse med., 1919, 27, 46, 
