HOMES AND DOMESTIC HABITS 71 
suffer the loss of their ‘own lives in protecting their off 
spring from enemies. Many mother birds have the instinct 
to flutter about a discovered nest crying and apparently 
broken-winged, thus leading the predatory fox or weasel to 
Fie. 165.—Nest and run-way of the pocket-gopher. 
fix hig attention on the mother and to leave the nest un- 
harmed. This development of parental care and protec- 
tion of the young reaches its highest degree in the case of 
the human species. The existence of the family, which is 
the unit of human society, rests on this high development 
of care for the young. 
