Physiology. — ''On the Hespinitory Movements of the Frog'. By 

 Piof. V. Wii,[,KM. (Coinmuiiicated l)v Prof. G. van Rijnberk). 



(Communicated in the meeting of March 23, 1918). 



Wlien j)re|)aring llie practical exercises given to students in l)iologj 

 at the Physiological Laboratory of Amsterdam, it appeared to me 

 that the numerous essays which the literatnre on the respiratory 

 movements of the frog offers, leave still several points nnexplained, 

 and that the technical experiments execnted by us furnished a more 

 exact insight into some particnlarities. 



I have namely registered better cnrves of the pressure in the 

 month-cavity than those whicli were hitherto obtained. The mano- 

 meter was bronght into this cavity through the ductus Eustachii, 

 after piercing the tympannm ; sometimes the experiment was applied 

 to frogs whose tongues had j)reviou8ly been removed. In other ex- 

 periments the tube was brought into the bncco-pharyngeal cavity 

 along the oesophagns. 



The pressure in the Inngs was registered according to the method 

 of Graham Bkown. At the same time the movements of the throat 

 were registered five times enlarged. During these experiments the 

 frog was lying on its back, and the lever was either erected as 

 for the snspension-cnrves of the heart, according to Engklmann, or 

 the animal was sitting in the normal squatting postnre, and the 

 registration was performed by means of a special apparatus which 

 I shall describe later on. 



As an example I commnnicate here a diagram demonsti-ating the 

 relations between the movements of the bottom of the mouth and 

 the moditications of tlie pressure in the bucco-pharyngeal cavity. 

 By means of a number of such like graphical representations 1 have 

 composed the following diagram of the synchronism in the pheno- 

 mena of the natural respiiatory ventilation ; in a more circumstantial 

 essay I shall explain the experimental data from which this scheme 

 has been composed. 



1. During the space of time (1 — 2) the pressnre in the lungs {P) 

 descends first qnickly, afterwards more slowly ; at the same time 

 the pressnre in the mouth-cavity, which was about (atmospheric 

 preesure) [B) rises to the same level (about 1 centimeter water). 



