TRANSACTIONS OF THE SECTIONS. 79 



On some Peculiarities in the Circulation of the Liver. By Alexander 

 Shaw, Surgeon to the Middlesex Hospital. 



The object of this paper is to treat of the influence of the actions of respiration 

 upon the circulation of the blood in the liver. Former writers have shown that, during 

 the act of inspiration, the cavity of the pericardium undergoes a dilatation ; a dispo- 

 sition for a vacuum to take place in the space around the heart, therefore, occurs at 

 that time; and the consequence is, that the blood in the venous trunks is drawn 

 with increased velocity to the right auricle. Sufficient attention, however, has 

 not been paid to the effect of this auxiliary power in promoting the free discharge 

 of blood from the hepatic veins, and thereby facilitating the circulation of the liver 

 generally. To prove that the blood is sent with increased velocity from this gland to 

 the heart during the act of inspiration^ the author directs especial notice to three prin- 

 cipal points, — first, to the place at which the venae cava? hepaticae join the inferior cava ; 

 secondly, to the structure of the hepatic veins; thirdly, to the mode in which the opening 

 in the tendon of the diaphragm through which these veins pass is enlarged orcontracted, 

 in correspondence with the motions of respiration. With regard to the first point, as 

 the hepatic veins join the cava inferior just where it has entered the cavity of the peri- 

 cardium, it follows that their mouths will be exposed directly to the influence of the 

 vacuum described as occurring at inspiration in that cavity ; secondly, as to the ana- 

 tomical characters of the venae cavae hepaticae, the peculiar structure of these veins 

 corresponds with the view that the blood is subject to be drawn out of them by the 

 force of suction. It is a law in physics, that for fluid to be propelled along a tube by 

 atmospheric pressure, it is a necessary condition that the tube communicating with 

 the cavity in which the vacuum takes place should be of a rigid structure, otherwise 

 its walls will become collapsed. The author first refers shortly to the mechanism 

 described by Sir Charles Bell*, as provided in the neck for protecting the veins in 

 that situation from the effects of the atmospheric pressure while the vacuum is form- 

 ing in the chest during inspiration, and then proceeds to point out that a provision 

 for the same object exists in the veins of the liver. He shows that, owing to these 

 veins being contained in canals, the boundaries of which consist of the firm substance 

 of the liver, and to the coats of the veins adhering closely to the interior of the canals, 

 whereby they are prevented from collapsing, they may l»e regarded as rigid tubes, 

 capable of resisting the atmospheric pressure. He considers, therefore, that when 

 there is a disposition for a vacuum to be formed in the cavity of the pericardium 

 during inspiration, and the liver is subjected to compression, the venae cava? hepaticae 

 are enabled, by this peculiarity of their structure, to maintain their calibres of the 

 natural size ; and the blood is consequently drawn, or pumped out of the depths of 

 the gland with accelerated velocity at that time f. Lastly, the author directs atten- 

 tion to the difference in the relative dimensions of the opening in the tendon of the 

 diaphragm, through which the hepatic veins pass, according as the muscular fibres of 

 the diaphragm are in a state of contraction or of relaxation ; and he likewise points 

 to the change in the direction of this opening, as compared with the orifices of the 

 veins of the liver, dependent on the shifting of the position of the parts in these two 

 conditions. During inspiration, not only is the opening in the diaphragm dilated, 

 owing to the tension of the tendon at that time, but, from the protrusion of the liver, 

 the veins are elongated, and their course made straighter and more favourable for the 

 escape of the blood ; whereas in expiration, the opening in the diaphragm is con- 

 tracted, owing to the relaxed and flaccid condition of the tendon ; and from the change 

 of position of the liver, the course of the veins from the point where they emerge from 

 the gland to that where they pass through the diaphragm, is rendered oblique, or a 

 kind of valvular obstruction takes place between the two openings. By these means 

 it follows, that while the force of suction is in operation during inspiration, the chan- 

 nel for the transmission of the blood is both wide and direct ; but that during expi- 

 ration, when from the contraction of the chest there is danger of the blood regurgi- 

 tating from the heart into the open canals within the liver, their mouths are partially 

 closed. 



* Practical Essays, Part I. 



t See the same subject treated of by M. Berard, Arch. Gen. de Med. 1826 ; also by Dr. 

 Carson, ' Inquiry into the Causes of the Motion of the Blood.' 2nd edition. 



