THE STAPHYLOCOCCUS GROUP 295 
the skin, and precautions must be taken to eliminate this source of 
error before makinji; cultm-es. 
(c) Animal Inoculation.— The virulence exhibited by staphylococci 
for animals is not a reliable index of their virulence for man. 
- Dissemination and Prophylaxis.— The wide distribution of staphylo- 
cocci on the nuicous niem])ranes, particularly on the skin and in the 
hair follicles, makes the prevention of their introduction to under- 
lying tissues through cuts and abrasions difficult. The customar\' 
procedures of aseptic surgery are the best preventives of infection. 
The skin may be sterilized for operation (after thorough cleansing 
and drying, which is imperative) by painting with freshly prepared 
tincture of iodine, or iodoform. Sterilization is usually accomplished 
within ten minutes after the iodine is applied. 
Staphylococcus Pyogenes Citreus.— This organism differs from 
Staphylococcus aureus chiefly in the color of the pigment it produces, 
a lemon yellow, and a lessened ability to liquefy gelatin. 
Staphylococcus Pyogenes Albus.— In many instances this organism 
is an achromogenic variant of Staphylococcus aureus; it produces 
white colonies on agar and gelatin, it liquefies gelatin slowly, and it 
is somewhat less pathogenic for rabbits; many strains do not ferment 
mannitol. 
Staphylococcus Epidermidis Albus.— Welch first described this 
organism, which appears to be a degenerate Staphylococcus albus; 
it does not liquefy gelatin and its pathogenic powers are practically 
nil. It frequently causes the troublesome but relatively benign 
"stitch abscesses." It appears to be a very constant parasite on the 
skin. 
Fig. 37.— Micrococcus tetiagenus. X 800. 
Micrococcus Tetragenus.- Micrococcus tetragenus was first de- 
scribed by Gaflfky;! he found it in cavities of the lung in pulmonary 
tuberculosis. It occurs but rarely in pure culture in abscesses either 
> Langcnbeck's Archives, 18S3, 28, 500. 
