ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 29 1 



particularly due to movements of the girdles, those of Cistudo are 

 especially due to the muscles diaphragmaticus and transversus abdominis 

 (expiratory) and obliquus abdominis (inspiratory). 



To these Couvreur adds the following results : — (1) The pause may 

 occur independently of the state of the glottis, — by the sustained con- 

 traction of the inspiratory muscles. It may occur in full inspiration, 

 or in half-inspiration ; but, ofienest, immediately after inspiration the 

 expiration begins, lasts long, and is followed by a pause when at its fulh 

 (2) Distinct movements of the plastron correspond to the respiratory 

 movements. (3) Below the larynx the pneumogastric contains especi- 

 ally the inspiratory fibres, or, more exactly, the sensory fibres producing 

 the inspiratory reflex. 



Respiration in the Frog.* — Prof. E. Couvreur corroborates Paul 

 Bert as to the following mechanism in the frog's respiratory process : — 

 (1) Lowering the floor of the mouth, the glottis being shut, the nares 

 open, entrance of air ; (2) Pause in lowering the floor of the mouth, 

 glottis open, nares open, contraction of flank muscles, passage of air 

 outwards by the nostrils (expiration) ; (3) Raising the floor of the 

 mouth, glottis open, nares narrowed, passage of air to the lungs (in- 

 spiration). 



He has registered the intra-buccal and the intra-pulmonary pressure^ 

 and finds that they do not quite correspond at given times. He concludes 

 that not all the movements of the buccal floor are true respiratory 

 movements, reacting on the lungs ; and that the true respiratory move- 

 ments are not all of the same value, some being especially inspiratory 

 and others expiratory. The lung is at first gradually inflated, then it 

 deflates intermittently. The opening and closing of the glottis permits 

 or prevents the elasticity of the lungs from asserting itself, and limits 

 expiration. 



This does not seem quite clear in summary, but a more concrete 

 statement is given. Suppose the lungs full of air ; a first contraction 

 of the abdominal muscles drives part of-this air out by the open glottis,, 

 during a pause with mouth-floor lowered ; this air passes out by the 

 nares. At the next raising of the floor, either the glottis is shut and 

 nothing enters the lungs, or only a little air enters, less in quantity than 

 that which has just come out. Soon a new abdominal contraction drives- 

 more air out from the lungs. This is repeated four or five times, till 

 the lung is completely deflated. Analogous movements continue, but 

 with this difference, that now more air goes into the lung than comes 

 out, whence the inflation of the lung. One may say that the expiration 

 occurs by instalments, and the inspiration likewise pauses, separating 

 the various periods, with a particularly long pause when the lung is at 

 its maximum inflation. 



In birds and mammals inspiration and expiration have the same 

 amplitude and occur without pause. In Amphibians and reptiles there 

 are almost always pauses ; inspiration gaining on expiration, the lung 

 inflates ; expiration gaining on inspiration, the lung deflates ; and the 

 pauses occur either at full inspiration or in half-expiration. We wish 

 that the author had been less terse in his statement, and we are not 

 sure that we have altogether understood his conclusions. 

 * Ann. Soc. Linn. Lyon, xlv.|(1899) pp. 1-4. 



