124 ANATOMY OF THE RABBIT 



ly shown in a cast of the cavity (Fig. 71). The suitability of the 

 term cah'x is evident. 



Fig. 71. Medial, dorsal, and posterolateral views of a cast of the renal 

 pelvis and beginning of the ureter of a rabbit. The deep depression visible 

 in the middle .of the cast in the posterolateral view is occupied by the renal 

 papilla. The pelvis is slightly distended by the pressure required to fill it 

 with the mass. 



Internal Structure and Function 

 When horizontally divided (Fig. 70), the kidney is seen to be 

 made up of a n:ore vascular and granular external layer, termed the 

 cortex, and of a somewhat radially striated, central mass, termed 

 the medulla. Notwithstanding the solid appearance of cortex and 

 medulla, the kidney is made up of a system of tubules, the relation 

 of which to the vascular system is such that water and certain 

 soluble substances to be excreted are passed into them from the 

 blood stream. The primary tubule, or nephron, (Fig. 73, B) 

 begins in each case in the cortical substance with a cup-like structure, 

 known as a renal or Malpighian corpuscle. This consists of a double 

 capsule containing a glomerulus or knot of capillaries from the 

 renal artery (Fig. 73, A). The blood in the glomerulus is separated 

 from the cavity between the two layers of the capsule only by a 

 very thin membrane composed of the lining of the capillary and 

 that of the capsule, both of which linings are uninterrupted, and 

 through this membrane fluid is filtered into the cavity of the capsule, 

 whence it flows into the tubule. The nephron beyond the capsule 

 is differentiated into portions known as the proximal and the distal 

 tubules. The first of these comprises a convoluted portion, a 

 straight portion, a thin portion, and a thick portion, of which the 

 first with the renal corpuscle lies entirely in the cortex while the 



