484 PHYSIOLOGY CHAP. 



vagus endings. This is easy in birds, whose lungs, as we know, 

 communicate via the bronchi both with the bony chambers, and 

 with the diaphragmatic, axillary, and abdominal air-sacs. These 

 last are highly developed ; on opening the body they are conspicuous, 

 and when they are pierced, and the walls of the abdomen held 1 

 apart by a blepharostat, the air from a gasometer, blown through 

 the trachea (under a gentle, regular, and continuous pressure), 

 escapes by the ventral opening. 



Bieletzsky (1881) was the first to attempt this experiment. 



FIG. 218. Gradual transition from normal respiration to apnoea, with continuous pulmonary 

 ventilation in turkey. (Luciani and Bordoni.) Ventilation commences at V at a pressure of 

 1 mm. Hg. Tracing recorded with a tambour with exploring lever .applied to sternum, con- 

 nected with a tambour with writing lever. 



He stated that he obtained perfect apnoea lasting for the whole 

 time of the inflation. But he made very few experiments; and 

 worse, he stopped half-way, omitting the most important part of 

 the research, i.e. that of seeing what effect was produced by 

 continuous inflation after the section of the vagi at the neck. 



We resumed these experiments with Bordoni at Florence 

 (1888). The following are the most striking of our results, the 

 full value of which, in regard to a general theory of respiratory 



Fio. 219. Continuation of previous tracing during prolonged period of apnoea. At point C 

 ventilation ceases, and there is a gradual return to normal respiration. 



rhythm, can be appreciated now that we have made a physio- 

 logical analysis of the various forms of apnoea. 



(a) In turkeys, continuous ventilation with intact vagi 

 constantly produces the apnoeic state. When air is insufflated 

 with Waldenburg's gasometric apparatus, at a pressure of 4-5 mm. 

 Hg, apnoea is instantaneously produced ; at a pressure of 2-3 mm. 

 Hg the transition from normal respiration to apnoea occurs, with 

 a distinct decrease in the respiratory acts, which is of brief 

 duration; finally, at a pressure of 1-1/5 mm. Hg the decrease 

 previous to apnoea is very gradual and prolonged (Fig. 218). The 



