626 LABORATORY EXERCISES 



LESSON 23 

 Walcr Analysis. 



I. Collect water from tap in a sterile Erlenmeyer flask, allowing H2O to run for 

 ten minutes before collecting. 



II. Melt two tubes of gelatin at 42°C. 



III. Add to tube No. A o.i c.c. and tube No. 2 0.2 c.c. from the flask. Shake 

 to mix H2O with gelatin. 



IV. Pour in Petri dishes No. A and B and place in locker. 



V. Count colonies which develop at end of twenty-four and forty-eight hours. 



VI. Estimate the number of colonies which would have developed in i c.c. of 

 water. 



Example. 



Twenty-four hours 



50 colonies have developed on plate No. A — 50 X 10 = 500 in i c.c. 

 96 colonies have developed on plate No. B — 96 X 5 = 480 in i c.c. 



2)980 



490 in I c.c. 



Forty-eight hours 



62 colonies have developed on plate No. A — 62 X 10 = 620 in i c.c. 

 102 colonies have developed on plate No. B — 102 X 5 = 510 in i c.c. 



2)1130 



565 in I c.c. 



LESSON 24 



METHODS OF IDENTIFICATION 



Descriptive Terms. — For complete details consult Eyre, J. W. H. : The Elements 

 of Bacteriological Technique, 1902: 208. 



Types of Colonies 



A. Size. — The size of the cells and the spores at various ages. 



B. Shape. — Punctiform, round, elliptic, irregular, fusiform, cochleate, amoeboid, 

 mycelioid, filamentous, floccose, rhizoid, conglomerate, toruloid, rosulate. 



C. Surface Elevation. — Flat, convex, capitate, umbonate, effused, pulvinate, 

 umbilicate, raised. 



D. Character of Surface.- — Smooth, alveolate, punctate, bullate, vesicular, 

 verrucose, squamose, echinate, papillate, rugose, corrugated, contoured, rimose. 



E. Internal Structure of Colony (Microscopic). — Refraction weak, refraction 

 strong, amorphous, hyaline, homogeneous, homochromous, finely granular, coarsely 

 granular. 



