494 



KIDNEY. 



[CHAP, xxxiv. 



Fig. 240. 



the capillaries of the Malpighiau tuft, enters the efferent vessel, 

 which conducts it into the branch of a portal vein ramifying upon 



thesurface of the lobule. 

 From the portal vein, 

 it passes into a system 

 of venous capillaries 

 surrounding the tubes, 

 from which it is at last 

 carried into the emul- 

 gent veins, which, with 

 the artery,lie in the cen- 

 tral part of the lobule. 

 " The comparison 

 between the hepatic 

 and the renal portal 



Part of fig. 239 shaded, showing the arrangement of the vessels Circulation may be 



and uriniferous tubes in the kidney of the boa, and in animals fur- , i -i 



nished with a portal vein from an extraneous source, a. Artery. tnUS Qrawn in more 

 /. Terminal twig going to Malpighian body. e f. Efferent vessel -, , rpr,~ 



of the Malpighian body emptying itself into a branch of the portal general terms. 1 116 por- 



vein, p v, on the surface of the lobe, b b. Ultimate branches of the , -i , * J.T__ V t , QT , 



portal vein entering the capillary plexus, p, surrounding the tai SySiem OI tne liver 



nriniferous tube, t. u. Branch of the ureter on the surface of the i i \-\ c 



lobe, e v. Emulgent vein within the lobe, receiving the blood from naS a QOU D16 SOUrCC, OUC 



the plexus surrounding the uriniferous tubes. Supposed to be ov 4-,. aT1|aniia fU P nfhpr 



magnified about 40 diameters. eXiraULOUfc., II1C ULIlt 



in the organ itself; so the portal system of the kidney, in the 

 lower tribes, has a two-fold origin, one extraneous, the other in 



the organ itself. In both cases, the 

 extraneous source is the principal one, 

 and the artery furnishing the internal 

 source is very small. But in the kid- 

 ney of the higher tribes, the portal 

 system has only one internal source, 

 and the artery supplying it is propor- 

 tionably large."* 



Of the Secretion of Urine. Having 

 passed in review the anatomical arrange- 

 ment of the different structures com- 

 posing the kidney, we shall now pro- 

 pian of the renai circulation in man ceed to consider briefly the functions 



and mammalia, a. Terminal branch of .,,!,: "U +Tn p> v pril nnrfe npvf 



the artery, giving the terminal twig af, WHICH tHC SCVCral parts perl 



to the Malpighian tuft, m, from which '4.1. VP o-arr! tn tVp MfllrnrrliiaTi tnffr<5 



emerges the efferent or portal vessel, ef Wlin regaiQ IO 1116 IViaiplglll [1 tUllS , 





Fig. 241. 



(not shaded). Other efferent vessels, t, nvp ^ rc >^A v op Pn that 1T1 nm'mals 1T1 

 e,e, e, are seen entering the plexus of nave dilLtluy b lldlSs, 11 



capillaries surrounding the uriniferous ,!, ;,-,>, f} 1fi nrinnrv PY^rPiriPTit i5 ra5SPfl 



tube, t. From this plexus the emuigent WHICH ttie urinary excrement is pass< 

 vein (r) springs. in an a ] most so \\& form, the tufts are 



* Phil. Trans., 1842. 



