MEDICINAL SUBSTANCES 1 99 



3. Mold spores. 



4. Yeasts. 

 Plating methods. 

 Colon bacillus test. 

 Tetanus bacillus test. 



Tests for the staphylococcus and streptococcus groups. 



In securing samples for examination, the precautions necessary 

 to guard against outside contamination must be observed. 

 Only rarely will it be necessary to pack the samples in ice. In 

 the preliminary routine of the laboratory, many of the more ex- 

 tensive contaminations will be apparent to the unaided senses. 

 Thus a change in color, in odor, in taste, and opacities in sub- 

 stances that should be clear, sediments in substances that should 

 be free from deposits, etc., generally indicate decomposition 

 changes due to bacteria and other organisms. More or less 

 cloudy deposits with a clear supernatant liquid indicate possible 

 spore sedimentation. Extensive contamination by bacteria, 

 yeasts and molds may be estimated quantitatively by means 

 of the hemacytometer and other suitable counting devices. 

 All are agreed that the counts for medicinal substances intended 

 for administration per mouth should not be very high. How- 

 ever, no numerical standards have as yet been adopted. It is 

 suggested that such remedial agents are unfit for use when they 

 contain bacteria in excess of 5,000,000 per cc. and yeasts and spores 

 in excess of 500,000 per cc. Plating methods should be resorted 

 to in order to ascertain the number of living bacteria present. 

 The potassium tellurite may also be tried in order to ascertain 

 microbic invasion. 



All substances containing gelatin, intended for hypodermic 

 use or for application to mucous membranes or to abraded skin 

 surfaces, should be tested for the anaerobic tetanus bacillus 

 {Bacillus tetani). Comparatively large quantities should be 

 plated in large Petri dishes or in Erlenmeyer flasks (using agar 

 media), and incubated at 37° C. in the absence of oxygen. Oxygen 

 may be excluded by pouring a layer of sterile olive oil over the 



