21 



attached could "be withdrawn through it. To the large trough a tray of the same 

 material was soldered. The tray was furnished with a circular hole about 1.5 cms 

 in diameter, in the bottom, the hole being covered with a glass slip cemented to 

 the metal by means of de Khotinsky's cement. A moist chamber consisting of two 

 parallel strips of glass was placed above this opening. To the top of these strips 

 was cemented a small glass tube bent into the shape of a horseshoe, h. (See figure 

 15). 



The whole apparatus was then mounted on a mechanical stage of a microscope by which 

 means it could be moved accurately. The circular hole in the tray was so arranged as 

 to be over the lens of the condenser. This sub-stage condenser had an especially 

 long focal distance for use with hanging drop preparations. The typs of microscope 

 used had a large curve in the supporting arm so that the trough containing the rat 

 fitted in snugly between the objectives and the microscope arm. The rat was anaes- 

 thetised with urethane, subcutaneously injected, and an incision made through the 

 right flank through which the gut and its attached mesentery could be withdrawn. The. 

 animal was then placed in the trough and the incision arranged opposite the rectangu- 

 lar hole in the side of the trough. The gut, g, was withdrawn with padded forceps 

 and the mesentery spread over the glass ring. Some drops of warm saline were then 

 placed on top of the spread mesentery and a round cover slip, c, applied. The surfac 

 tension at the interface between the mesentery and the glass caused the former to be? 

 flattened out on the under side of the coverslip. The tray was filled with saline, 

 which also ran into the moist chamber so that the mesentery was kept moist from 

 above and below. The whole apparatus was placed in a warm box during the period of 

 observation. This apparatus was constructed so that the capillary vessels could be 

 manipulated from below by means of a Chambers' micro-dissection apparatus. fSee 

 figure 15). Plorey, 1926. Landis 1925-26. Wearn and Richards, 1924-25. Vfhite and 

 Schmitt 1926. 



8. MICBOELECTRODES. 

 A. ETTISCH AND PETERPI. 



A non-polari sable microelectrode has been developed by Ettisch and Peterfi. Its 

 construction is as shown in figure 16, where (l) is the agar-filled capillary 

 with miCro-tip, (2) the holder for capillary, (3) the agar filled T-tube, (4) 

 the calomel electrode, (5) the Bakelite holder, and (6) the wire leading to the 

 electrometer. The micro-electrode is fastened as pictured in the diagram. The 

 capillary itself is constructed and filled with agar as shown in figure 16, A-P, 

 in which (A) is the empty capillary, (B) the agar (in N/lO KC1) sucked in to fill 

 central portion of the capillary, (C) one end sealed in flame, (D and E) the other 

 end pulled out to form a micro-tip, (P) agar forced to tip by warming. The shank 

 end is then broken off. Major difficulties which beset the preparation of the 



F M^te^w.altt a*^ 



Ti* 16 



