XII 



MECHANICS OF EESPIRATION 



429 



pressure equal to - 80, during inspiration equal to - 102 mm. 

 of water. 



The simplest method for recording the oscillations of intrathoracic pressure 

 in animals is to introduce into the oesophagus, after previous oesophagotomy, 

 an elastic sound, or hollow metal tube, covered at one end with a fine rubber 

 membrane, which is connected with a writing tambour, after ligation of the 

 oesophagus (Fig. 192). This last operation is necessary to ensure the perfect 

 occlusion of the oesophagus above the exploring sound, while beneath it the 

 tonicity of the cardiac orifice is 

 sufficient to guarantee closure, save 

 at the moment of deglutition, which 

 rarely occurs in the narcotised 

 animal. The imperfect closure of 



the oesophagus, after introducing 

 id 



FIG. 1 !>:>. Luciani's oesopliageal explorer. Elastic 

 sound, covered at the end with fine rubber 

 sheath. 



the sound by the mouth or nostril, 

 makes it difficult to obtain these oscillations of intrathoracic pressure in 

 man (Rosenthal). It might be possible to remove this inconvenience by 

 the expedient employed by Pfliiger and Ludwig in their -pulmonary catheter 

 (Fig. 170, p. 388). 



Bert's method may be employed for recording the in tra-abdominal pressures. 

 This consists in the introduction into the rectum of a glass tube, fixed against 

 the anal sphincters by a kind of pessary to make it air-tight, and connected 

 with a water manometer and writing tambour (Fig. 193, A). The inter- 

 vention of a manometer is, however, superfluous, 

 and no special contrivance is required to ensure 

 closure of the anal orifice, which was sufficiently 

 guaranteed by the tonic contraction of the 

 sphincters. The same object can be effected by 

 the introduction of a short length of urethra! 

 catheter of large diameter, perforated in several 

 places,' and provided at the ends and centre 

 with three circular ridges formed of rubber 

 rings, over which is drawn a thin, membrane 

 (Luciani). This method is applicable toyman, 

 and is invariably successful, so long as the 

 precaution is taken of emptying the intestine 

 of the faeces accumulated at the lower end 

 (Fig. 193, B). 



FJG.IDS. Rectal explorers Bert (A) 

 and Luciani (B). A, Glass tube, 

 open at the end, which is in- 

 troduced into the rectum and 

 plugged in anal aperture by in- 

 flation of a hollow elastic pessary 

 joined to the tube. B, Elastic or 

 metal sound, with two lateral 

 openings, fitted with three rubber 

 rings, covered with a small fine 

 sheath. 



XL Whatever the absolute values 

 of these oscillations of pressure in the 

 two body cavities determined by re- 

 spiratory rhythm, it is evident that they 

 must have a considerable influence on the centripetal course of 

 the blood in the veins, and be an effective aid to the circulation 

 as controlled by the heart. 



This physiological doctrine is fairly ancient. Valsalva (1760) 

 and Haller (1766) seem to have been the first who observed on 

 man the swelling and emptying of the jugular vein coincident 

 with expiration and inspiration. David Barry (1825), from the 

 aspiration of coloured fluid along a tube fastened centrally in the 

 jugular, formed an exaggerated notion of the functional importance 

 of inspiratory thoracic aspiration. Wedemeyer (1828) repeated 



