CHAPTEE XVII. 



ACUTE EXANTHEMATA. 



THE specific causes of the various exanthematous diseases 

 are unknown. That these diseases are due to bacteria can- 

 not be doubted. They are highly contagious, and run a course 

 which corresponds to the life-cycle of an organism. By 

 exercising the usual precautions observed in all diseases hav- 

 ing a bacterial cause, the spread of the exanthemata is pro- 

 hibited. All cases have their origin in some other case, so 

 that the exciting cause cannot be otherwise than bacterial. 

 Furthermore, one attack confers an immunity which under 

 ordinary conditions is permanent. 



Measles : In measles the most frequently occurring organ- 

 ism has been a coccus obtained from the blood of patients 

 sick with measles. Its specificity has not been proved, how- 

 ever. The contagium is contained in the nasal mucus, the 

 conjunctival secretion, the sputum, and the blood. Contact 

 with the sick is necessary before infection can occur. Measles 

 is rarely conveyed by clothing or carried any great distance. 

 Children are more susceptible to the disease than adults, but 

 when adults are infected the disease usually runs a very severe 

 course. One attack confers immunity. 



Scarlet fever : The virus of scarlet fever is much more 

 virulent than that of measles. 



Infection may occur even months after recovery, from 

 handling the clothing or anything else that the patient may 

 have used during his illness. Direct contact with the con- 

 tagious element is necessary. Infection usually occurs through 

 the respiratory tract. The scales appear to play a very 

 important role in conveying the disease, but just how is still 

 a matter of conjecture. 



Streptococci and diplococd of various kinds have been 

 found in the blood and scales of scarlet fever patients. The 



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