THE KIDNEY TRACING 193 



mixture and then the lid is rubbed down into close contact with the edge. 

 The lateral tube is now connected by thick-walled rubber tubing to the 

 recording tambour. In the rubber tubing is inserted a T-piece, the lateral 

 orifice being closed by a rubber tube clamped by a spring clip. The tambour 

 now shows the oscillations due to the heart beats. The oncometer must now 

 be tested to see if it be air-tight by blowing in a little air through the T-piece 

 into oncometer and tambour. The tambour lever is raised and the pressure 

 of air inside is greater than atmospheric pressure. If the tambour lever fall 

 there is a leak, and the oncometer must be reopened and the packing more 

 thoroughly carried out. If the tambour lever remain at the same mean 

 level the experiment may be proceeded with. The whole abdomen is thoroughly 

 covered up with warmed layers of dry cotton wool, the abdominal wall 

 having been previously drawn together by sutures. 



The cannula in the carotid is now connected to the mercury manometer 

 and the writing points brought to the recording surface. The procedure of 

 the remainder of the experiment can be varied in different ways according to 

 circumstances. 



The following five paragraphs give the course of an experiment 

 which will show the main facts to be gained by the method. The 

 results obtained are examined in the succeeding pages : — 



1. Having brought the air pressure inside the oncometer to 

 atmospheric pressure, by opening for an instant the clip on the lateral 

 pass of the T-piece, take a piece of normal tracing. 



2. Inject 1 c.c. of a 4 per cent, solution of caffeine citrate in 1 per 

 cent NaCl. To do this fill the cannula and rubber tubing in the 

 external jugular vein with the solution by means of a pipette drawn 

 out to a fine point. Fill a 1 c.c. pipette with the solution and attach 

 to the cannula by rubber tubing. Take a short piece of normal 

 tracing and removing the bull-dog forceps from the central end of the; 

 vein, at a given signal blow in 1 c.c. of the solution. Eeplace the 

 clamp on the vein. The instant of injection is marked on the tracing 

 by means of a signal. If this dose be not sufficient repeat with an 

 increased dose until a typical effect is produced. 



3. After complete recovery from the caffeine citrate inject 5 c.c. of 

 a 0*1 per cent, solution of digitalin in 1 per cent. NaCl. Previously 

 remove the caffeine solution still in the cannula by sucking it up in a 

 pipette drawn out to a fine tube, which can pass down the cannula ; 

 then wash out with normal saline, remove the saline, and fill with the 

 digitalin solution. Attach a pipette containing 5 c.c. of the new 

 solution and inject at a given instant. 



4. Inject 1 c.c. of a solution of neurine made by adding one drop 

 of a 25 per cent, solution of neurine to 5 c.c. of 1 per cent. XaCl. 

 The cannula is to be washed out and filled with the solution as in S. 



5. To complete the experiment, record the kidney changes during 



asphyxia. Dissect out the trachea, open it widely, and while a tracing 



is being recorded suddenly plug it tightly with cotton wool soaked 



in water. 



o 



