PERFUSION OP VESSELS. LYMPH-HEARTS 



87 



with Ringer's solution containing acid (HC1, 1 in 5000) and alkali 

 (NaOH, 1 in 5000), with a very dilute extract of suprarenal, and 

 with solutions of chloroform and ether in Ringer's solution. Normal 

 Ringer's solution must invariably be substituted afterwards for that 

 containing the drug, and a third determination made in the same 

 way (average of three counts). 



The same method is used for perfusion of the organs of mammals. The can- 

 nula is tied into the artery of the (excised) organ, which is placed in a jacketed 

 funnel warmed to 40 C. : the perfused 

 fluid, which must also be warmed before 

 entering the organ, escapes by the vein and 

 runs down the funnel into a measuring 

 vessel. In this way perfusion can be con- 

 ducted through the kidney of the dog or 

 sheep, or through the vessels of a limb. 

 In the case of mammals it is important to 

 allow oxygen to bubble through the Ringer 

 solution used for perfusion. 



Methods o recording the outflow of 

 fluid. 1. The sequence of drops can be 

 recorded by aid of an electric drop re- 

 corder connected with an electro- magnetic 

 signal, which writes upon the smoked paper 

 of a drum. 



2. Another method of graphically re- 

 gistering the rate of flow, especially if the 

 drops follow one another too fast to be 

 recorded individually by a drop-recorder, 

 is furnished by the " tilter " shown dia- 

 gramniatically in fig. 73. This is a small 

 vulcanite or celluloid trough with open 

 ends with a septum across the middle ; 

 the trough is balanced on a vulcanite knife- 

 edge. The drops are led over the middle, 

 and, falling on the side of the septum 

 which happens to be uppermost, they 

 gradually fill that side of the trough. 



When full, it overbalances, and the trough tilts over to the other side, when 

 the process is repeated. Each double movement of the tilter is registered, either 

 by an electrical or a pneumatic arrangement, upon the recording paper, on which 

 the time is also written. The capacity of the tilter being known, the amount 

 of fluid flowing in a given time is ascertained. The record will continue auto- 

 matically for long periods. 



The above methods are also used to record the flow of secretions 

 (Chapter XXII.). 



Lymph-hearts. Place a frog the brain of which has been destroyed, or which 

 has been decapitated, in the prone position on the frog-cork, and reflect the skin 

 from either side of the urostyle. Notice the pulsation of the lymph-hearts 

 beneath the fascia on each side : usually they do not synchronize. Destroy the 

 spinal cord completely by a wire. The lymph-hearts now cease to beat : their 

 pulsations are dependent on the spinal cord. 



FIG. 73. DIAGRAM OF TILTER. THE ROCK- 

 ING MOVEMENTS ARE RECORDED EITHER 



BY ALLOWING THE ACCUMULATED FLUID 

 TO ACTUATE A TAMBOUR, OR BY AN 

 ELECTRO-MAGNETIC SIGNAL. 



