MEASLES. 575 



quently occurs in persons who have not come in direct contact with 

 either the blood or secretions of measles patients, but have only been 

 near those affected with the disease, we cannot doubt that the conta- 

 gion is also contained in the emanations from the skin and lungs. 

 From some very striking observations of Panum, it has been proved 

 that this contagion in the atmosphere can, without losing its activity, 

 be carried for miles by the body and clothes of healthy persons who 

 have been near a patient, and who are not themselves attacked by the 

 disease. The period of incubation lasts from ten to fourteen days. 

 In one epidemic of measles that I carefully observed, of which Dr. 

 Pfeilsticker has given some very interesting accounts in his disserts 

 tion, written under my superintendence, school-children only were at 

 first affected, and exactly ten days later, after the latter remained 

 home from school, a. large number of smaller children, who had been 

 infected by their brothers and sisters, were attacked. In some cases, 

 particularly where the infected person is already suffering from some 

 other disease, the period of incubation appears to be somewhat longer. 

 To the question, When is measles infectious ? with our present 

 knowledge, we should say that it is most infectious while the eruption 

 is out ; that it is probably not infectious in the stage of desquamation, 

 while numerous cases speak for its being so in the prodromal stage 

 The popular opinion, that measles is most catching in the desquamative 

 stage, arises from inattention to the period of incubation. A child in- 

 fected by its brother or sister breaks out with the disease while the 

 latter is desquamating, it is true, but was infected while the exan- 

 thema was at its height, or, perhaps, even before the eruption. The 

 probability of infection during the prodromal stage is supported by 

 the wonderful spread of measles through schools. Great care is 

 usually taken to keep out of the school any children who have not 

 gotten through the desquamative stage, as well as those having any 

 suspicious exanthema ; but children with catarrh and cough are al- 

 lowed to sit on the seat with well children. If the disease were only 

 transferred by the former class, it would be quite impossible to under- 

 stand why, during an epidemic of measles, a school is often entirely 

 emptied, while the children attending another school are not affectec? 

 oy the disease. The predisposition to measles is very extended. Al- 

 most every one has the disease once during life ; but one attack al- 

 most invariably exhausts the susceptibility to new attacks. Since 

 measles occurs quite frequently in populated countries, most persons 

 are attacked during childhood, and have lost the predisposition when 

 they are grown up. It is only in this sense that measles can be called 

 a disease of childhood. Of 196 children, under fourteen years of age, 

 that had not had the measles, who lived in a small town near Ttibin- 



