PRESIDENTIAL ADDRESS. Th 
In answer to the second question, it may be stated that it 
is possible, if not absolutely certain, that the two diseases 
are due to different organisms. 
In answer to the third question, it 1s quite possible that 
if the etiology of rat leprosy were thoroughly worked out 
we would find the solution of the human leprosy problem. 
This leads to a very interesting, and possibly very im- 
portant, speculation. There are several diseases known, 
affecting man and animals, due to acid-fast bacilli, probably 
really species of Streptothrix, and quite a number of dis- 
eases due to other streptotriches and allied organisms. 
Tuberculosis in human beings, bovines and other animals, © 
is due to the various varieties or species of tubercle bacilli 
which by some are called Streptothrix tuberculosis. The 
disease affecting the intestines of cattle, causing thickening 
of the ruge, and known as Johne’s disease, is also due to an 
acid-fast bacillus. Dr. Bull met with a case of this disease 
in an imported cow in Melbourne in 1911. Then we have 
human leprosy and rat leprosy, all of these diseases being 
due to acid-fast bacilli of the Streptothrix group. 
In addition we have, as a common disease in cattle and 
an occasional disease in man, actinomycosis, which in cattle 
may be responsible for ‘‘lumpy jaw’’ and ‘‘ wooden tongue.”’ 
This disease is due to the growth of various species of 
Streptothrix or allied fungi, and there seems no doubt at all 
but that the infection is conveyed to the animals from their 
surroundings (herbage, ete.). This is indicated by the fre- 
queney with which awns of grass or similar material are 
found in cases of the disease whether in animals or human 
beings. From this it would appear that infection in ac- 
tinomycosis occurs ‘from the surroundings of the animals 
or human beings, where presumably the fungi responsible 
are living saprophytic existences, rather than by direct con- 
tamination from previous cases. 
