. The anatomy of the salamander. Salamanders; Salamanders. THE RESPIRATORY SYSTEM, INCLUDING THE LARYNX 275 involves only the air contained in the mouth and pharynx. This is known as bucco-pharyngeal respiration. The second is more compli- cated and involves the lungs, so that it is conveniently referred to as pulmonary respiration. More recently Willem (1923 and 1924) has carried out experi- ments on the respiratory movements of the mouth-floor of a large number of Amphibia, both Urodele and Anuran, including Sala- mandra, and has taken tracings of these movements by means of a stirrup placed
. The anatomy of the salamander. Salamanders; Salamanders. THE RESPIRATORY SYSTEM, INCLUDING THE LARYNX 275 involves only the air contained in the mouth and pharynx. This is known as bucco-pharyngeal respiration. The second is more compli- cated and involves the lungs, so that it is conveniently referred to as pulmonary respiration. More recently Willem (1923 and 1924) has carried out experi- ments on the respiratory movements of the mouth-floor of a large number of Amphibia, both Urodele and Anuran, including Sala- mandra, and has taken tracings of these movements by means of a stirrup placed under the head and attached to a pointer. (Text-figs. I, 2, and 3 are taken from his work.) Text-figure i is one. Text-Fig. i. A tracing of the movements of the floor of the mouth, taken by means of a stirrup passing under the head, reading from right to left. The ordinates are magni- fied by 5 and the speed is 4 mm. per sec. The change in the level of the tracing is due to a movement of the head. (After Willem.) Text-Fig. 2. A tracing of the periodic variations in the amplitude of the pulmonary expirations. Read from right to left. (After Willem.) such tracing in which the ordinates, representing the amplitude of the oscillations of the mouth-floor, are magnified by five, the ribbon at the same time passing under the needle at the rate of 4 mm. per second. The movements involved in pulmonary respiration are represented towards the right-hand side of the figure as a deep de- pression in the otherwise more or less regular succession of bucco- pharyngeal movements. Text-figure 2 shows that there is a rhythmic variation in the amplitude of the pulmonary respirations, while text- figure 3 is an enlarged detail of one series of movements involved in filling and emptying the lungs. According to Willem the bucco- pharyngeal respirations occur at the rate of 120 per minute and have an amplitude of nearly 2 mm. The interval between successive pul- monary respirations depends on circums
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