446 PROF. AV. N. F. WOODLAXD ON LIGATURING THE 



on August 19tli only weiglied 14'6 gins, (after alio wing for weight of food in gut). 

 All internal organs were quite healthy, and. the renal afferent veins were very large, 

 due of eourse to the small size of the newly-formed portion of the anterior ahdominal. 

 The heart had apparently become nuich reduced in size, or was naturally small, the 

 ratio being (weight of body at date of operation) 325"0 ; the liver was also extremely 

 small (ratio=67'2) ; and the kidnet/s ivere below the average size (ratio=260"0). 



Summarizing the results of these experiments, we may conchide 

 tliat the ligature of the anteiior abdominal vein caused either 

 the death of the animal or the re-formation of the anterior 

 abdominal vein : in no case did an animal svarvive in a healthy 

 condition for a considei-able length of time without a functional 

 anterior abdominal vein. 



Conclusions. 



The fact that a new anterior abdominal vein was always formed 

 in those toads which survived the operation described is no proof 

 that the suj^ply of blood to the liver by this vein is essential to 

 the animal, because, as I have already pointed out, this feature is 

 most certainly due to the fact that the arterial circulation in the 

 kidneys is interfered with under the conditions of these experi- 

 ments, and that is a sufficient reason for the formation of a neAV 

 anterior abdominal vein. 



We have also seen that frogs can live without the blood in tlie 

 anterior abdominal vein being added to that in the hepatic portal 

 vein, and this fact by itself is good evidence for the view that the 

 non-gut blood is not essential to the animal's welfare. 



Two questions remain : (1) why should an anterior abdominal 

 vein exist? and (2) why should it normally open into the hepatic 

 portal vein ? The answer to the first question I have ah'eady 

 indicated in a paper* published in 1906. In this paper I 

 contended that in animals with " portal " kidneys the flow of 

 blood through the primitive posterior cardinal veins is considerably 

 hindered by the kidney tubules inA'ading the lumina of the two 

 veins and subdividing them up into coarse networks of sinusoids 

 (Shore t, Minot J ), and that the anterior abdominal vein is formed 

 as an altei-nativeroutetorelieve the congestion consequent on the 

 formation of the " renal portal " system. Judging from recent 

 measurements of the relative diameters of the renal afferent and 

 anterior abdominal veins in Bufo siomaticics and Buna tempoj'aria 

 respectively, I find§ that in the Indian toad about three-fifths of 

 the venous blood from the legs flows to the heart via tlie anterior 

 abdominal vein and about two-fifths via the two renal afferent 

 veins, and that in the frog {B. temporaria) about one-half of the 

 blood flows by each of these two routes, from which we may 

 conclude that the resistance to flow of the blood ofiered by the 

 liver capillary system is in the toad about one-third and in the 

 frog about one-half of that offered by the renal venous meshwork 

 (" renal portal "' system) of each kidney. From other evidence§ 



* Woodland, W. N. F., Proc. Zool. Soc. London, 1906, p. 886. 

 t Shore, T. W.. Jour. Anat. Physiology, vol. xvi. (n.s.) 1901. 

 J Minot,C. S., Proc. Boston Soc. Nat. Hist. vol. xwiii. (10) 1898, p. 265. 

 § See Part 11. of my paper " Cu tlie ' Renal Portal ' System etc.," shortly to be 

 published. 



