ELEMENTARY DEMONSTRATIONS 



139 



CHAPTER XXXVII. 

 RESPIRATION CONTINUED. NERVOUS CONTROL OF RESPIRATION. 



Record of the Respiratory Movements of the Diaphragm. Head's 

 Method. DEMONSTRATION. A rabbit is anaesthetised with urethane or 

 chloral. The skin is divided over the ensiform cartilage. One blade 

 of a pair of scissors is passed carefully under the cartilage, and the latter 

 is severed from the sternum. Two slips of muscle pass from the central 



Fio. 121. --Tambour recorder. The muscle 

 is attached to the hook and pulls against a 

 spring. The lever compresses the tambour. 

 This tambour is connected with a recording 

 tambour. 



FIG. 122. Tracheal cannula for artificial 

 respiration. The slit at the side, the size of 

 which can be controlled, allows the air to 

 escape in expiration. 



tendon of the diaphragm to the ensiform cartilage. One end of a liga- 

 ture is tied on to the cartilage and the other end to a lever. The lever 

 pulls against a spring and presses against a receiving tambour. The 

 contraction of the muscle slips can be recorded by connecting the 

 receiving with a recording tambour. A thread, carrying a small flat 

 button, is passed on either side through the diaphragm and the walls of 

 the thorax, between the fifth and sixth ribs. As soon as the two threads 

 are tightened the buttons become pressed against the tendonous ends of 

 the muscle slips and fix them to the anterior wall of the thorax. The 

 threads are knotted together over the front of the sternum. 



A tracheal cannula is inserted. Note the effect of blowing air several 

 times in succession into the lung and of sucking air out of the lung. 

 Positive ventilation provokes expiratory spasm, negative ventilation 

 expiratory relaxation of the diaphragm. Next note the effect when the 

 vagi are divided. The division of one vagus has but Jittle effect on the 

 respiration. If the divided central end of the nerve be allowed to fall 

 back into the wound it may be stimulated by its own action-current, 



