Physiology. — ‘Muscle Sound in Birds’. By Miss L. Kaiser. 
(Communicated by Prof. G. van RIJNBERK). 
(Communicated at the meeting of April 3C, 1921). 
Concerning muscle sound and action currents in birds I found no 
data except a provisional communication by Wiss *), which as far 
as I know has not been followed by a more ample one. Weiss 
recorded the sound of the m. pectoralis of a pigeon by means of 
a very thin membrane, the pigeon being poisoned with strychnine. 
He so obtained a curve in which the distance between two crests 
varied from 5 to zs second. The action current of the same 
muscle in similar conditions showed waves of a duration of #5 to 
z+ second, which agrees perfectly with the values mentioned above. 
SCHWARZKOPF ®) found, as other investigators (Margry, Ricner, and 
Exner) had found before him, that the number of stimuli necessary 
to produce complete tetanus for pigeon muscle is 70 to 125 per 
second. Pürrrr?) mentions 70 to 80 per second as the greatest 
number of separate contractions possible in bird’s muscle. 
Ewarp *) has described a vibration, which he observed in pigeons 
and in a few other birds at the upper edge of the orbita and at 
the eyeball. He supposes a simultaneous contraction of both the m. 
obliqui to be the cause of this vibration and calls the phenomenon 
‘“Augenschwingen’’. By means of a lever, attached to the head of 
the pigeon and resting upon the upper edge of the orbita, as well as 
by means of a double needle with writing apparatus fixed into the 
eyeball, Ewanp succeeded in recording this phenomenon. The curves 
obtained by these two methods practically confirm each other, the 
rate of the waves being 25 to 30 per second. 
The same phenomenon was further examined by the author. 
The vibration, which may be observed by touch, over the whole head 
of the bird, is also very evident to the ear. A phonendoscope 
placed upon the head of the pigeon conducts to the ear a low 
sound, in which a tone of a low pitch may be distinguished. 
1) Centralblatt f. Physiol. Bd. 26. 1912. 
3) Pflüger's Archiv. Bd. 121. 1908. 
5) A. Pürrer, Vergleichende Physiologie, 1912. 
4) Archiv. f. experiment. Pathol. u. Pharmakol. Suppl. 1908. Festschrift ScHMIEDE- 
BERG. 
