626 Proceedings of the Royal Irish Academy. 



4. Varieties of Entrance. ^Th.e places where renal arteries enter 

 the kidney vary. Usually — (a), all enter at the hilum ; (/3), one often 

 enters at the lower end, and this in most cases comes from the aorta, but 

 may be a branch of the normal renal, once from the lumbar ; (y), one 

 may enter at the upper end, most commonly a branch of the supra- 

 renal, but "which may be from the aorta or normal renal. I have seen 

 a vessel piercing into the front surface of the gland from the normal 

 renal ; and in another case a posterior branch passed under the inner 

 edge of the gland, and entered the gland at the middle of its posterior 

 surface. 



5. Varieties of Distriiution of Branches. — From the renal there may 

 arise branches- — {a), to the supra-renal capsule, very common if not 

 normal ; (f), to the diaphragm, once ; (c), to the right cms of the 

 diaphragm; ((?), to the right colon; [e), to the pancreas, deep surface 

 of the head; (/), to the testis, supplanting the normal spermatic; 

 {g), to the right lobe of the liver. These anomalous branches, with 

 single examples of which I have met, were all on the right side, 

 which is curious, as the majority of the anomalies in Class No. 2 were 

 sinistral. 



In connexion with these anomalies, it is interesting that in one 

 case of Oppolzer's anomaly, a floating kidney, where the organ was 

 almost entirely surrounded with peritoneum, the vessels were normal, 

 as in the case described by Urag (Wiener Medicinische Woehenschrift, 

 857, No. 42). 



Multiplication of renal arteries is not surprising when we consider 

 the arrangement of these vessels in other animals and their develop- 

 ment. Thus for the elongated kidneys in fishes the arteries are 

 numerous, and with a trace of metamerism in their succession. In 

 the iguana and monitor, among lizards, they are also multiple, as also 

 in snakes. The alligator and crocodile have three or four on each 

 side. Most birds have four, five, or six pairs, of which the three 

 uppermost arise from the aorta, and the two or three lowest from the 

 ischiatic. 



The mammalian kidney is the metanephros, or hinder part of the 

 primitive excretory organ, and it originates from a rounded mass of 

 mesoblast, from the intermediate cell mass at that region where the 

 dorsal outgrowth from the "Wolffian duct extends forward to the tissue 

 behind and nearer the spine than the rest of the nephros. In this tissue 

 the vessels originate in situ in the mesoblast, close to those which 

 supply the abdominal wall. These vessels, which are thus close 

 together, separate at an early period, though traces of this primitive 

 relation persist in the extra -peritoneal anastomoses of the renal ar- 

 teries, through their arterise adiposte and capsular branches. We owe 

 many of the anomalies above described to persistent accidental enlarge- 

 ments of some of these vessels. 



