358 
J. T. NATTRESS. 
thromboses performed, and the microbes be permitted to locate 
and multiply. In other words, to locate a pre-fistular abscess 
there must be furnished a locus tninoris usis tentice, which Senn 
defines as being an area of lesser resistance, due to a tissue 
injury which so changes the tissue that pathogenic microbes, 
previously present in the circulation, become arrested and 
find favorable conditions for multiplication. But recent tis¬ 
sue lesions are not the only factors which may serve to 
produce such an area of lesser tissue resistance. The pres¬ 
ence of old pathological products, exposure, feeble perform¬ 
ance of an organic function, and a variety of general and 
illy-defined factors, seem to produce conditions favorable to 
local infection. 
The regions which fistula usually select are such as are 
liable to receive blows and bruises, given by angry attendants, 
received by passing under low sheds, or through low door-ways, 
or while rolling. Again, the soft tissues of these parts are 
mainly connective, and connective tissue areas are very prone 
to chronic suppurative processes and slow healing. Such, then, 
are the factors which serve to locate suppurative processes. 
There yet remain many questions regarding the history and 
work of pyogenic microbes for bacteriologists and chemists to 
answer. We all wish to know to what depth beyond the sur¬ 
face of a pyogenic membrane do these pus-producing germs 
reach. Why does pus burroiv? Is it by pressure and absorption? 
or is it due to some mysterious part played by the microbes in 
their effect upon protoplasmic cell contents. We do not know 
so much as we would wish regarding the tendency of suppura¬ 
tive processes. Fistula sometimes heal rapidly and abscesses 
develop in the atlo-axoid region. 
There are some strange features in such cases. Why do not 
domestic animals other than solipeds develop fistula ? 
Treatment .—Many annoying features in the treatment of 
these cases, which may be well understood and yet difficult 
to handle, for example, the well-known tendency to recur after 
indefinite periods of apparent soundness. 
