446 



PROF. W. N. F. WOODLAND ON LIGATURING THE 



on August 19tli onl}'- weighed 14*6 gms. (after allowing for weight of food in gut). 

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

 due of course to the small size of the newly-formed portion of the anterior abdominal. 

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

 ratio being (weight of body at date of operation) 325*0 ; the liver was also extremel}^ 

 small (ratio —67'2) ; and the Tcichiei/s tvere below the average size (ratio = 260'0). 



Summarizing the results of these experiments, we may conclude 

 that the ligature of the anterior abdominal vein caused either 

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

 abdominal vein : in no case did an animal survive in a healthy- 

 condition for a considerable length of time without a functional 

 anterior abdominal vein. 



Conclusions. 



The fact that a new {interior abdominal vein was always formed 

 in those toads which survived the operation described is no proof 

 that the supply 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 new 

 anterior abdominal vein. 



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

 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 vshould 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 already 

 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 invading the lumina of the two 

 veins and subdividing them up into coarse networks of sinusoids 

 (Shore t, Minot;]: ), and that the anterior abdominal vein is formed 

 as an alternative route to relieve 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 siomaticus and Rana temporar ia 

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

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

 abdominal vein and about two-fifths via the two renal afli'erent 

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

 blood flows by each of these two routes, from which w^e may 

 conclude that the resistance to flow of the blood oflfered 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. 

 X Minot, C. S., Proc. Boston Soc. Nat^ Hist. vol. xxviii. (10) 1898, p. 265. 

 § See Part IF. of luy paper " On the ' Renal Portal ' System etc.," shortly to be 

 published. 



