1918] Grinnell: A Synopsis of the Bats of California 231 
Tt is not, of course, to be inferred that all the free end-knobs function alone 
as pressure perceptors, for, as is well known, the sensory nerves of the human skin 
mediate at least four different qualities of sensations, namely, pressure, warmth, 
cold, and pain. But the number of nerve end-knobs in the skin is so great, and 
the latter in the bat is so sensitive to delicate tactile stimuli, that the number 
of free nerve terminations in the epidermis functioning as pressure perceptors 
must necessarily be very large. 
I have repeatedly watched captive bats, of several species, when 
loosed in a many-windowed room, and though they were clearly seek- 
ing a means of escape, not one was ever seen to dash against a window 
pane, as does a bird under like circumstances. These bats were in 
full possession of the faculties of sight and hearing. To judge from 
the actions of birds similarly situated, neither faculty could apprise 
these creatures of the fact that glass is an impenetrable barrier. The 
only theory which seems adequately to explain the bats’ recognition 
of the invisible barrier, glass, is that condensations (pressures) of 
the atmosphere set up between the window-pane and the bats stimu- 
late sensory structures in the integument of the bats, as suggested by 
Ackert, or possibly, in the internal ear, as Hahn considered probable. 
According to Barrett-Hamilton (1911, p. 42), we must give Cuvier 
eredit for this theory. He says: ‘‘It seems that Cuvier was not far 
wrong when he wrote that ‘it is by means of the pulsations of the 
wines on the air that the propinquity of solid bodies is perceived, by 
the manner in which air reacts upon their surface.’ ”’ 
Smell—Hahn (1908, p. 154) suggests that since bats catch their 
food in the air where a flying insect leaves no permanent path and 
cannot be definitely localized by its odor we must infer that the bat 
in seeking food does not rely on its sense of smell. But he adds: ‘‘It 
must not be inferred... that the sense of smell is lacking, or even 
rudimentary. All bats have a strong odor, the purpose of which is 
probably to attract others of their kind. This may be taken as an 
indication that smell is well developed, for otherwise the odor would 
be useless.’’ The same author enumerates several instances in which 
captive bats failed to locate food which could have been found only 
through the sense of smell. 
Taste —I can find no statements concerning a sense of taste among 
bats except the very general one by Barrett-Hamilton (1911, p. 28): 
“Tn captivity practically all insects are accepted except those which 
are distasteful to insectivorous animals generally.’’ 
