THE SENSE OF SMELL IN BIRDS 635 
tap (fig. B). Gentle air currents were forced into each com- 
partment through glass tubing arranged as seen in fig. b. The 
air currents were produced by a machine originally constructed 
for injecting blood vessels. In this apparatus (fig. D), water 
was passed from one closed tank into another by elevating the 
filled tank above the empty one. The two tanks were connected 
Text fig.C Diagram of labyrinth; A, B, C, D, chambers; d, position of entrance 
to main enclosure (m. e.) from cage; f. b., food box. 
by rubber tubing (r.t., fig. D). The air displaced by the entering 
water in the lower tank was allowed to escape through stop cocks 
into two glass tubes. Each of these tubes communicated with a 
wash bottle (one-litre size) which was about three-fourths full 
of water. From the wash bottles, the air emerged through T 
tubes (fig. A, tt.) and was conveyed to 125 ec. bottles (fig. A, 
b’) opposite the four chambers of the labyrinth. These smaller 
