328 CLINICAL BACTERIOLOGY. 



investigations have been made with variola and with calf- 

 lymph. In spite of all the efforts that have been made the 

 exciting agent of smallpox has not yet been discovered. It 

 is possible that it does not at all belong to the class of 

 bacteria, and in any event its requirements of the culture- 

 media are different than are those of the bacteria whose 

 gowth has thus far been successful. On ordinary bacteri- 

 ologic examination staphylococci, pseudo-diphtheria-bacilli, 

 and rarely streptococci are found in animal lymph. It has 

 been maintained by Landmann that the evidences of irrita- 

 tion that are sometimes apparent in marked degree around 

 the pustules are due to the activity of these pyogenic cocci. 

 On the other hand, the Commission for the Investigation 

 of the Vaccine Question ( 1 896) emphasized that the staphy- 

 lococci found were of moderate, and only exceptionally of 

 considerable, pathogenicity for animals, and that virulent 

 streptococci could no longer be found in the lymph after 

 the lapse of eighteen days. The streptococci found in 

 older specimens are to be looked upon as only harmless 

 skin-epiphytes, such as can not rarely be isolated from bac- 

 terial mixtures. Frosch, the reporter of the Commission 

 mentioned, reached the conclusion that no etiologic relation 

 exists between the bacteria of the lymph and the irritative 

 and inflammatory manifestations of the inoculation-pustule, 

 and that in the preparation of animal lymph any noteworthy 

 reduction in the number of germs or their complete exclu- 

 sion even with the observance of strict antisepsis is not 

 attainable ; that, therefore, it is impossible to obtain an 

 unirritating lymph-supply. 



Varicella (chickenpox) has nothing to do with the ex- 

 citing agent of variola and of vaccinia, and recovery from 

 the disease does not protect against smallpox. 



ACUTE EXANTHEMATA. 



The exciting agents of the acute exanthemata are, like- 

 wise, thus far unknown. 



Measles is contagious in an extraordinary degree. The 

 susceptibility of human beings to the disease is exceedingly 

 great between the second and tenth years of life ; it is less 

 in the first year and in adults. Natural immunity to measles 

 practically appears not to occur. The contagium is con- 



