34 MOSQUITOES OF NORTH AMERICA 
confidently termed the second joint the “auditory capsule.” His studies were 
evidently influenced by his knowledge of the structure of the vertebrate ear, not 
only in the interpretation of the anatomical structure of the organ, but, in con- 
sequence, also of its functions. Probably inadequate microscopes and methods 
contributed in large part to his errors. He described what he found as follows: 
“The auditory capsule is filled with a fluid of moderate consistency, opales- 
cent, and containing minute spherical corpuscles, and which probably bears the 
same relation to the nerve as does the lymph in the scale of the cochlea of higher 
animals. The nerve itself of the antenna proceeds from the first or cerebral 
ganglion, advances towards the pedicle of the capsule in company with the large 
trachea which sends its ramifications throughout the entire apparatus, and, 
penetrating the pedicle its filaments divide into two portions. The central 
threads continue forward into the antenna and are lost there; the peripheral 
ones, on the contrary, radiate outwards in every direction, enter the capsule 
space, and are lodged for more than half their length in sulci wrought in the 
inner wall or cup of capsule. 
“In the female the disposition of the parts is observed to be nearly the same, 
excepting that the capsule is smaller.” 
Assuming the conditions to be such as described it was very natural to at- 
tribute to the organ complex functions. Johnston sums up his reasons for be- 
lieving the antenna an auditory organ of high perfection as follows: 
“The position of the capsules strikes us as extremely favourable for the per- 
formance of the function which we assign to them; besides which there present 
themselves in the same light the anatomical arrangement of the capsules, the 
disposition and lodgment of the nerves, the fitness of the expanded whorls for 
receiving, and of the jointed antenne fixed by the immovable basal joint for 
transmitting vibrations created by the sonorous modulations. The intra-cap- 
sular fluid is impressed by the shock, the expanded nerve appreciates the effect 
of the sound, and the animal may judge of the intensity, or distance, of the 
source of the sound, by the quantity of the impression: of the pitch, or quality, 
by the consonance of particular whorls of the stiff hairs, according to their 
lengths ; and of the direction in which the undulations travel, by the manner in 
which they strike upon the antenna, or may be made to meet either antenna, in 
consequence of an opposite movement of that part.” 
A. M. Mayer, in the course of his researches in acoustics, made most interest- 
ing experiments with the supposed auditory function of the antennal hairs of 
the male mosquito. With tuning-forks, he showed that some of the hairs are of 
such a structure that they vibrate in response to sound-waves numbering 512 per 
second. Other hairs vibrated to other notes, showing altogether a considerable 
range. He says: 
“T infer from my experiments on about a dozen mosquitoes that their fibrils 
are tuned to sounds extending through the middle and next higher octave of 
the piano.” 
Mayer carried his experiments farther, and, taking accurate measurements of 
the thickness and length of two hairs which vibrated in response to the tuning- 
forks Ut 3 and Ut 4, made large wooden models of them. The model of the 
hair vibrating to the Ut 3 tuning-fork was a meter in length. These models 
responded to vibrations of approximately the same number as the hairs them- 
selves. 
