234 PROFESSOR TURNER'S ACCOUNT OF THE GREAT FINNER WHALE 



paucity of the system of arterial arcades, the proximity of the intestine to the 

 aorta, the pressure, from the elastic recoil of the arterial wall, of the enormous 

 column of blood in the aorta, would seem to render some mechanical arrange- 

 ments necessary, by means of which that pressure may be distributed and 

 regulated before the blood enters the slender arteries within the wall of the 

 intestine. 



The structure of the moniliform tube admirably adapts it for this purpose. 

 The blood flows through it on its way to the intestinal arteries, and is diffused 

 into the numerous dilatations or bays which bulge out from its sides. The 

 transverse inflexible folds on its inner wall diminish at intervals the lumen of 

 the tube, and where they project so far as to leave but a narrow aperture in 

 the axis of the tube, they act as strictures in retarding the flow of the current. 

 At the same time their circular arrangement enables them to act as internal 

 girders, and to strengthen the walls so as to prevent over distension of the tube* 



I have already referred to the analogy between the rete mirabile in the cetacea, 

 and the network in connection with the intra-cranial arteries in the pig. I may 

 now allude to a modification which the pig exhibits in the arrangement of its 

 mesenteric arterial system. The arteries subdivide in the middle of the mesen- 

 tery, and form there a compact network — a rete mirabile — from which numer- 

 ous small arteries radiate outwards to the intestine.t These radiating vessels 

 closely correspond in appearance to those which I have described as arising 

 from the moniliform tube in the Longniddry whale. The Cetacea, therefore, 

 present affinities to the Pachydermata, not only in the diffused character of the 

 placenta, but in the possession of closely allied modifications of the cerebral 

 and intestinal arterial systems. 



The presence of a moniliform tube, in connection with the intestine, does 

 not seem to have been previously recognised in the Cetacea by anatomists. 



The superior vena cava was formed by the junction of the two innominate 

 veins, on the right of the ascending aorta. Each innominate vein began at the 

 root of the neck in the form of a dilated sinus, into which the veins from the 

 neck, flipper and inner wall of the chest opened. The inferior cava received 

 a number of hepatic veins before it pierced the diaphragm. The umbilical vein 

 was 27 inches long in the foetus in its course from the umbilicus to the 

 liver. 



The portal vein in the foetus had a diameter of 3 inches before it entered 



* My colleague, the Professor of Engineering, Professor Fleeming Jenkin, to whom I pointed out 

 the structure of this tube, concurs in the opinion of its function expressed in the text. 



t The mesenteric rete in the pig has long heen known to anatomists — see Barclay on the 

 Arteries, Edinburgh, 1812; T. J. Aitki in Reports of Edinburgh Meeting of British Association, 

 1834, p. 681 ; Owen, Comparative Anatomy of Vertebrates, vol. iii. ; Gurlt, Anatomie der Haus- 

 saugethiere, Berlin, 1860. The complexity of the rete in the pig is due to the plexiform arrangement 

 of both the mesenteric vein and artery. 



