DR. MILLER CORROBORATES DR. ABBOTT. . 299 



have changed but very little since they were given to the dental 

 profession in 1879), I will take the liberty of quoting from men who 

 have written on this subject since that time. Dr. "W. D. Miller 

 (Berlin) says: "A mixture of 68.0 grams saliva x 1.0 bread, 0.5 

 meat x 0.5 sugar, kept for 48 hours at the temperature of the human 

 body, generated more than sufficient acid to decalcify the entire 

 crown of a molar tooth. * * * There remains still to be an- 

 swered the questions : Do bacteria ever penetrate directly into per- 

 fectly sound enamel or dentine, and do they perform any part in the 

 decalcification ? I have already referred to the gradual diminution 

 of the bacteria in number as we go from the outer to the inner mar- 

 gin of the preparation (i. e., from the surface to the deeper parts of 

 the dentine), till at the inner border but few or none of the tubuli 

 are found to be infected. This fact, which leads us to the conclu- 

 sion that the micro-organisms cannot penetrate beyond that point 

 to which the tissue has been softened by the action of acids may be 

 readily confirmed by the examination of the softened tissue taken 

 from different depths of the cavity of a carious tooth. * * * 

 The microscopic examination showed the decayed part to be filled 

 with bacilli and micrococci, but riot in a single case have I found 

 them to pass beyond the softened (carious) into the sound dentine. 

 This, mind you, in sections of dentine so thin that they were readily 

 examined with a power of from 1,000 to 1,500 diameters. In teeth 

 of poor structure (poorly calcified) are found numerous irregular mi- 

 croscopic cavities (interglobular spaces). These cavities frequently 

 communicate with one another, and, through cracks or fissures, 

 with the surface of the tooth, in which case they may become filled 

 with micrococci. The latter are completely confined within the 

 cavities, and do not penetrate the normal dentine, * * * Pieces 

 of perfectly sound dentine, handled with great care, so as to be kept 

 as free as possible from all foreign matter, were placed in small vials 

 and covered with a drop of distilled water. These were then in- 

 fected with leptothrix, bacilli, and micrococci from decayed tooth- 

 bone, and kept at a temperature of from 35 to 38 C. Now, if the 

 organisms were capable of decalcifying the tooth substance, we 

 should expect (1) a softening of the tooth-bone; (2) the infection of 

 the softened part; (3) an increase in the number of bacteria and 

 cloudiness of the liquid ; (4) since the bacteria could accomplish the 

 decomposition only through the generation of an acid, we would 

 expect an acid reaction of the liquid. These vials were watched for 

 four months. For the first few days an increase in the number of 



