522 



REPORT— 1897. 



AB represents a cell composed of two parts, AA and BB, and made 

 of wood or glass. The square BB is firmly fixed on to a flat glass basis, 

 and through two of its sides run and are firmly fixed glass tubes CC, 

 opening into the space enclosed by the four sides of the cell. 



The movable top AA has a central circular aperture of about an inch 

 diameter, and to its under surface is fixed by some adhesive a large 



Fig. 2. 



coverslip (see line in diagram), so that when AA is placed on BB and 

 clipped down we have a cell into which the tubes CC open. 



The following sketch (fig. 3) will show how it is used in conjunction 

 with the required vapour : — 



The nerve is dissected out and lightly stretched on the under surface 

 of the cover glass on the cover AA, which is then placed on BB, so that 

 the nerve comes to be inside the cell. One tube C is then connected by 

 rubber tubing with a wash-bottle containing water, the purpose of which 

 is to keep the vapour moist as it passes over the nerve. The wash-bottle 

 is connected with a WoolfF's bottle containing ether or chloroform, and 



ETHER OR 



CHLOROFORM 



BELLOWS. 



fitted with the bellows commonly supplied to freezing microtomes, to 

 vaporise the ether. 



In studying the efiect of COg a Kipp's apparatus is fitted on in place 

 of the ether bottle and bellows. The cell can be placed under a low or 

 high power of the microscope, and the changes observed simultaneously 

 with the passage of the vapour. 



For the observation of the fresh nerve simultaneously with the passage 

 of the vapour, it is convenient to employ nerves as small as possible. The 

 nerves chosen for this purpose were usually the long slender cutaneous 

 filaments seen on opening up the skin of the frog's back. They possess 

 the advantages of being small, and are removable in considei'able lengths 

 for observation with a minimum of damage, as they lie comparatively free 

 in the subcutaneous lymph space. 



