THE BACTERIA OF THE NORMAL HUMAN BODY. l6l 



numerous bacteria, especially micrococci, and moulds. The 

 staphylococcus pyogenes aureus, the streptococcus pyogenes, 

 the bacillus pyocyaneus and the bacillus coli communis some- 

 times occur on the skin. According to Welch, it always con- 

 tains the staphylococcus epidermidis albus, which may be a 

 form of the staphylococcus pyogenes albus. This organism is 

 of some importance to surgeons on account of its relation to 

 the cleansing of the skin before operations. It seems impos- 

 sible, by any amount of cleaning, to dislodge all of the germs in 

 the skin especially those under the nails. 



The bacteria of the exposed mucous ~ membranes like the 

 conjunctiva* and the nasal cavityf and the mouth cavity 

 naturally fluctuate both in quantity and quality; they consist, 

 in fact, of those which happen to fall upon the surface or are 

 drawn in from the external air. 



In the mouth, however, there is a certain group of organisms 

 more or less characteristic of it, many of which have not been 

 successfully cultivated. These have been thoroughly studied 

 by Miller, to whose works students are referred. J 



Several species of spirilla have been discovered in the mouth 

 and are found along the margins of the gums. The leptothrix 

 buccalis, and related organisms which have a long, ribbon-like 

 form, also occur in the mouth. The micrococcus lanceolatus 

 (or pneumococcus) is present in many human mouths. In 

 15 to 20 per cent, of human mouths this organism is sufficiently 

 virulent to produce fatal septicemia when inoculated into 

 susceptible animals. Pyogenic bacteria, especially streptococci 

 occur frequently, although not regularly, in the mouth. Strep- 

 tococci very commonly occur on the tonsils. Putrefactive 



*Randolph, Pusey, Gifford. Journal American Medical Association. Oct. 

 3, 1903. 



fHasslauer. Die Bakterienflora der gesunden und kranken Nasenschleim- 

 haut. Centralblatt fur Bakteriologie. Vol. XXXIII. 1902. Orig. p. 47- 



t Miller. Microorganisms of the Mouth. For a review on the bacteria of 

 the mouth, see Madzar. Centralblatt far Bakteriologie. Vol. XXXI. Ref. 

 p. 489. Vol. XXXII. p. 609. 



