Figure 32. — Secondary entry or bolt hole. Note that there is no dirt deposited about the hole. At the time of its formation 
such a hole forms the termination of a previously blind tunnel segment. All of the dirt excavated up to the time of the 
formation of such a bolt hole is removed from some other entry. 
\< 10 FEET >| 
Figure 33. — Orientation in buirow construction. The tunnel between these two boxes parallels the trail connecting their 
drain tile entries (see fig. 14). Prior to the union of these two boxes by this tunnel, they were inhabited by rats of the 
same local colony which interchanged members. This is the connection existing between boxes 30 and 31 on December 21 , 
1948 (fig. 58), before they were excavated on the 22d and 23d. 
34 
