THE COMMUNICABLE DISEASES 485 
there are sufficient examples within important orders, 
and second, upon percentage of total cases. For the 
analysis of the pathological types, headings of probable 
origin, gross anatomical lesions and visceral distribution 
were then made. The first vertical column shows the total 
autopsies per order, and where families are given, for 
each of them. In three instances Primates, Ungulata 
and Galli, not all families are represented, so that the 
total for the order is greater than that for the subdi- 
visions quoted. It is noteworthy that we have had no 
tuberculosis among nine families of ungulates ; this will 
be discussed later. The second column gives the total 
cases of tuberculosis for the order and family, respec- 
tively, followed by a third line of percentages. For the 
analysis of the pathology in these animals all the proto- 
cols were reviewed. Forty-eight of them being found 
unsuitable, deductions were made according to the natural 
group, thereby leaving the number shown in the fifth 
column for separation according to origin and type. 
Analyses in the succeeding columns are made upon 
number of cases and not upon percentages, because of the 
confusion arising from small decimals. The actual rela- 
tionships will be pointed out in the notes. Percentage is 
not so necessary because comparisons and contrasts are 
usually made with classes or orders where the figures 
are comparable. 
It is generally conceded that the principal and only 
significant routes of origin for tuberculosis are via the 
respiratory and alimentary tracts. The criteria upon 
which to decide the route that has been followed are by no 
means definite and may not be for any given case 
unexceptionable. In birds the alimentary tract is con- 
ceded to be the important one, while in mammals an 
aerogenic route is believed to be the rule. However, since 
feeding experiments have shown that tubercle bacilli can 
gain the lungs by passing through the intestinal wall and 
abdominal lymphatics without leaving gross traces, the 
