106 SAPROPHYTISM, PARASITISM AND PATHOGENISM 
types of organisms which incite infection in association with the 
particular organs or tissues where they become locaKzed. It is import- 
ant in this connection, however, to remember that a great majority 
of progressively pathogenic bacteria exhibit rather marked affinities 
for special tissues, and that they invade the tissues through definite 
atria. The organisms which are habitually parasitic, on the contrary 
— "the opportunists"— as Theobald Smith has so clearly pointed out, 
are less exacting in this respect, as a rule, and they may invade the 
tissues whenever the natural barriers— skin, mucous membranes and 
so on— weaken and become vulnerable. 
The following table indicates the more common and important 
bacteria, parasitic or pathogenic, which may invade the tissues, and 
the organs where they tend to localize and develop. 
Skin: 
Staphylococcus and streptococcus groups. 
Acid-fast group: tubercle bacilli, lepra bacilli, smegma bacilli. 
Anaerobic group: tetanus, gas bacillus. 
Anthrax, plague, tularemia. 
"Bottle" bacillus (spore of Melassez).i 
Nose, Throat and Adnexa: 
Staphylococcus group. 
Streptococcus and pneumococcus group: scarlet fever streptococcus. 
Diphtheria and pseudo-diphtheria group. 
Influenza and pertussis group. 
Pneumobacillus, rhinoscleroma and ozena group. Perez bacillus. 
Bacillus fusiformis and spirillum group. 
Meningococcus and catarrhalis group. 
Acid-fast group — chiefly tubercle bacilli and leprosy. 
Blastomycetes and hyphomycetes. 
Virus of poliomyelitis, lethargic encephalitis and unknown viruses, mumps, etc. 
(Organisms of dental caries and pyorrhea not included above.) 
Eye and Ear: 
Streptococcus and pneumococcus group. 
Staphylococcus group. 
Diphtheria and pseudo-diphtheria group. 
Influenza group. 
Koch- Weeks and Morax-Axenfeld group. 
Gonococcus. 
Proteus group. 
Pyocyaneus group. 
Lungs: 
Streptococcus and pneumococcus group. 
Pneumobacillus group. 
Staphylococcus group: Micrococcus tetragenus. 
Acid-fast group: tubercle bacillus. 
Influenza and pertussis group. 
Plague bacillus, anthrax bacillus and B. psittacosis. 
Colon and tyi^hoid group. 
Actinomyces and hyphomycetes. 
Pelvic Organs: 
Streptococcus and staphylococcus group. 
Gonococcus and Treponema pallidum. 
Tubercle bacillus and smegma bacillus. 
Micrococcus (Bacillus) melitensis. 
1 See Dold: Parasitology, 1910, 3, 279, for literature. 
