244 



THE AMERICAN MONTHLY [November, 



rubber tube and the inserting a bit of grass rod into its end to prevent 

 the escape of the air. Then by gentle manipulation the distended lung 

 is brought upon the plate, B, Fig. 7. The ring containing a cover- 

 glass is then carefully lowered on the lung so as to produce a flat sur- 

 face. 



The frog-plate containing the animal prepared by one of the above 



methods is then placed 

 on the stage of the mi- 

 croscope. Sometimes 

 it is found upon exami- 

 nation that a stasis has 

 occurred in the blood 

 current. This may be 

 due to the shock of the 

 operation or it may be 

 caused by the abdomi- 

 nal walls compressing 

 the organ. If this trou- 

 ble be due to the first 

 cause the circulation 

 will soon be renewed ; 

 if to the latter, which 

 may be determined 

 after a lapse of a few 

 minutes, it must be re- 

 moved by enlarging 

 the abdominal wound 

 so as to relieve the 

 pressure. 



If the time of the 

 observation is t o be 

 short, fifteen to twenty 

 minutes, it will only 

 be necessary to wet the exposed organ, from time to time, with 

 normal salt solution. If this time is exceeded, then the animal is 

 to be covered with a piece of filter-paper wet with the salt solution 

 and the organ is irrigated with the same solution. The appai'atus for 

 irrigation is shown in Fig. 9. It consists of a litre bottle attached to a 

 ring-stand, the bottle being about half filled with normal salt solution 

 and its mouth closed with a rubber cork through which two glass tubes 

 pass. To the curved tube is attached a long piece of rubber tubing, 

 which is connected with the irrigating canula, g, Fig. 7 ; the straight 

 tube is for regulating the pressure in the bottle, which may be varied 

 by raising or lowering the tube. The flow of the irrigating fluid from 

 the end of die canula should be by drops at short intervals, and is reg- 

 ulated by the pressure in the bottle, the size of the opening in the points 

 of the canula, and if necessary by a screw clip placed on the rubber 

 supply tube, the screw clip allowing the lumen of the tube to be reg- 

 ulated at will. By the use of this apparatus observations may be con- 

 tinued for hours if the animal is kept paralyzed by the administration 

 of fresh doses of the curara. 



Prof. Thoma has also devised a piece of apparatus for studying the 



Frog-plate and Irrigating Apparatus. 



