The collection and examination of pus 103 



simple stain, such as carbol thionin. A specimen should also be 

 stained by Gram's method and the results compared. 



When cultural examinations are required, the best plan is to 

 make stroke cultivations on agar in the manner described on 

 p. 16, and incubate them for twenty- four hours at the temperature 

 of the body. The appearances of the colonies will be similar to 

 those described as occurring in cultures made from the blood, to 

 which the reader is referred. It is to be noted, however, that the 

 gonococcus will not grow under such circumstances unless the 

 surface of the medium has previously been coated with blood. 



Another method is to make gelatin plates. This is a very 

 simple matter if the materials are at hand. 



Requisites. — i. Two or three tubes of gelatin. 



2. Two or three sterilized Petri dishes. 



3. A platinum needle— a loop will be best. 



Process.— Inoculate a gelatin tube in the manner described on 

 p. 16, and then melt it by immersion in warm (not hot) water. 



Distribute the pus throughout the melted gelatin by rolling the 

 tube between the hands, and by tilting it from side to side. Do not 

 shake, and do not let the melted gelatin touch the cotton-wool plug. 



Take a loopf ul of the gelatin and transfer it to a second culture- 

 tube. Melt the gelatin in this and mix as before. Proceed to 

 inoculate a third tube from the second one if you think it probable 

 that the pus is very rich in organisms. 



Now take the first tube and singe the projecting part of the 

 wool plug, and heat the mouth of the tube in order to destroy any 

 germs which may be upon it ; allow it to cool. 



Place the Petri dish on the table in front of you, and raise the 

 lid sufficiently to allow you to insert the end of the test-tube ; do 

 this, and tilt the latter so that the melted gelatin flows into the 

 dish. Immediately replace the lid, and tilt and roll the dish until 

 the gelatin forms an even film over its whole lower surface. 

 Place it on a flat table to set. Repeat the process with the other 

 tubes. Incubate at about 20° C. for two or three days. Examine 

 the dishes, placing them on the stage of the microscope and using 

 the low power. Each organism will have grown into a small 

 colony, which will resemble those which are described in the 

 section on the blood. There will be slight differences, but not 

 enough to lead to error if the examination of the colonies is 

 supplemented by an inspection of stained films. 



The pneumococcus, gonococcus, the fungus of actinomyces, and 



