88 BACTERIOLOGY. 



Diagnosis brane. It is not safe to rely solely upon the presence 

 and appearance of a membrane, because membranes 

 may be due to infection with micro-organisms other 

 than the diphtheria bacilli, such as the staphylococcus 

 and streptococcus. In order to say whether a mem- 

 brane is due to diphtheria or not, a sterile cotton swab 

 is rubbed over the membrane, and then rubbed on the 

 surface of a tube containing coagulated blood-serum. 

 The tube and swab are now sent to the laboratory and 

 incubated at body temperature for twelve or twenty- 

 four hours in order to allow the bacteria present to 

 multiply. The growth is now smeared on glass slides, 

 stained, and examined under the microscope. If 

 diphtheria bacilli are present they can be readily 

 identified by their appearance. 



the'dteease The disease is spread to others chiefly by means 



of the bacilli thrown from the nose or mouth by 

 coughing and sneezing. The sputum contains the 

 bacilli in large number. Indirectly the disease is 

 spread from the sputum by means of clrinking-cups, 

 handkerchiefs, door-knobs, and among children from 

 pencils, chewing gum, toys, and other things that are 

 handled and passed about. Cats, rats, and mice may 

 carry the infection, and flies may deposit it on food 

 and milk. Infected milk has been the cause of a num- 

 ber of epidemics. 



Duration The most important and first precaution to be 



quarantine taken in limiting the spread of diphtheria is quarantine. 

 This means the complete isolation of the sick person. 

 The length of the quarantine cannot be determined by 



