HAEMODYNAMICS. 79 



Experiment 35. 



BLOOD PRESSURE. NERVE CONTROL OF HEART BEAT 

 AND PERIPHERAL RESISTANCE. HAEMORRHAGE 

 AND TRANSFUSION. INSPECTION OF HEART. 



1. PREPARATION OF ANIMAL. Weigh the animal. In the case of 

 dogs, inject morphine solution (sulphate or hydrochloride) sub- 

 cutaneously (0.5 c.c. of 2% solution per kilo of body weight). In 

 the case of cats, pass the stomach tube and pour the required amount 

 of ure thane solution into the stomach. (Give 1 gram of urethane 

 per kilogram of body weight, dissolving it in water to make a 20% 

 solution). These preliminary operations are to be performed by 

 the laboratory technician or by a demonstrator, with the students 

 assisting. In about one half hour the animal, now practically un- 

 conscious, is completely anaesthetised by administering ether. To 

 do this pour about 20 c.c. on a towel and hold this firmly over the 

 muzzle of the animal, being careful however to avoid suffocation. 

 The animal is then tied, back down, on the animal board, mean- 

 while deep anaesthesia is maintained by giving ether. Count the 

 pulse at the femoral artery; count the respirations and record the 

 rectal temperature. Note any peculiarities about the animal 

 (e.g., enlarged thyroid). 



While the operator and anaesthetist are preparing the animal 

 and performing the necessary operations, the technician and 

 other members of the group proceed to get the manometer tubing 

 and cannula ready, as directed in par. 3 below. 



2. INSERTION OF TRACHEAL CANNULA. Moisten the hair in front 

 of the neck and make a median incision down to the trachea (cut 

 with the edge, not with the point of the scalpel). Pass a stout 

 ligature under the trachea. Make a transverse incision half way 

 across the trachea, insert the tracheal cannula and tie it by means 

 of the ligature. The tracheal cannula is inserted to facilitate 

 artificial respiration should this be necessary. If further anaes- 

 thetic is required, connect the tracheal cannula with the wide- 

 mouthed anaesthetic bottle containing some ether. 



3. INSERTION OF CAROTID CANNULA AND RECORDING OF MEAN 

 ARTERIAL BLOOD PRESSURE. Pull apart the skin flaps and separate 

 the sterno-mastoid and sterno-thyroid muscles so as to expose the 



