574 



disturbed for a longer tiirie ilian the centres of respiration, motion, 

 etc. The same retardation wliicli is caused hj narcosis also manifests 

 itself if the fish is exposed lo the action of an electric current. 



We shall now try to investigate the course of the iniiibitory 

 sphincter reflex. 



GuYENOT stales that in tench, carp, etc. a delay in the manifestation 

 of the reflex could he observetl if the connection between the 

 forepart of the air-bladder and the perilymphatic space of the 

 vestibulary apparatlis, which is formed by the so-called bones of 

 Weber, was interrupted. If this view is correct, the function or at 

 least one of the functions of the bones of Weber mnst consist in com- 

 municating to the brain modifications in the gas-tension of the bladder. 

 Air-bladder -|- organ of Weber must be looked upon, in accordance 

 with the views of Hasse, Bridge and H addon and others, as a hydrostatic 

 organ. In this hydi'ostatic organ the ditctus-sphincter acts as a 

 safety-valve by means of which a surplus of gas may be removed. 



GuYÉNOT states that the emission of air-bubbles before the destruction 

 of this connection, set in at a pressure-decrease of ± 4.5 centimetres 

 of mercury ; immediately aftei- the operation it took place only after 

 a decrease of i'2 — J4 centimetres of mercury. 



In my preceding article (these Proceedings Vol. XXIII, p. 857) I 

 took exception to the technics of Guyénot's experiments. I feel 

 compelled to do the same now. Guyénot's method is open to various 

 objections. It is based upon the most distal of the bones of Weber, 

 the Tripus, being detached from the side of the air-bladder; the 

 reaction of the fish is investigated immediately after the operation, 

 and the fish is killed immediately after this investigation. 



Why was only the connection between air-bladder and Tripus 

 removed? Could not the air-bladder when it expands effect a pressure 

 on the Tripus, which could be transmitted to the vestibulary apparatus 

 by means of the rest of the organ of Weber? Why should the 

 fishes be killed immediately after the operation? Was it abso- 

 lutely impossible then that the retardation of the reflex was due to 

 the shock? Why was it not verified, in the case of some fishes at 

 least, that they reacted a few days after the operation exactly as they 

 did immediately after? 



These considerations induced me to test Guyénot's experiments. 



In two ways I tried to disrupt the connection in question. First 

 by making a ventral median section; thus I reached the body-cavity 

 and by moving a little hook past liver, intestine and genitals I tried 

 to destroy the connection. The sinus venosus rendered this operation 



