222 MICROBES, FERMENTS, AND MOULDS. 
We do not think that the dual nature of human - 
diphtheria, indicated by the researches of Klebs and 
Loffler, is yet established. The symptoms, and still 
more the histological lesions of this disease, are in 
favour of its unity, and it may be owing to other 
causes that the disease is more or less severe. 
The well-known polymorphism of microbes leads 
us to think that the bacilli represent the adult form, 
and the micrococci, or Microsporon, the early form of 
a single species, which is in all cases the cause of 
diphtheria and of its several manifestations—croup, 
diphtheria, etc. Further researches are necessary to 
decide this question. 
Whooping-cough and Influenza — Burger has 
lately discovered rods in the form of an 8 in the 
sputum of whooping-cough; they are found in great 
numbers in the white scum, and are even visible to 
the naked eye, and, like many other bacteria, they 
can be stained by methyl violet. To this microbe 
whooping-cough and its relapses are due, and it is 
always present. It has not yet been cultivated. 
Influenza resembles whooping-cough in the course 
it takes, and is probably also caused by microbes. 
Letzerich has found micrococci in the blood, to which 
he ascribes this disease, but his researches must be 
repeated with greater care. 
Certain facts observed in medical practice have 
led to the surmise that whooping-cough may be re- 
garded as an attenuated form of croup, just as vaccinia 
