240 OUTLINES OF EQUINE ANATOMY. 



ponent structures. A horizontal incision displays centrally 

 a cavity lined with mucous membrane, pelvis. Externally a 

 reddish-mottled smooth surface, cor?fzcaZjJorh'o%, andbetween 

 the two, the medullary ijortion, which is apparent to the 

 naked eye as consisting of tubular fibres, radiating from 

 the central cavity to the cortical portion. By microscopic 

 examination we may find that these tubes, hibuli uriniferi^ 

 are continued into the cortical portion, when they be- 

 come much convoluted, forming the tuhidi contorti, and 

 finally terminate in blind dilated extremities, Malijigliian 

 capsules. 



The branches of the renal arteries after division and 

 subdivision by traversing the medullary part, and breaking 

 up in their course gain the cortical portion, where as small 

 afferent vessels they run to the Malpighian corpuscles of 

 which they push the mucous membrane before them, caus- 

 ing it to bulge towards the commencement of the tubulus 

 uriniferus, for they exert their pressure at a point opposite 

 to this. On entering the depression of the wall of the cor- 

 puscles thus produced, the vessel breaks up into smaller 

 branches,which divide and reunite producing the glomerulus 

 or Malpighian tuft, from which arises the efferent vessel, 

 which emerges from the depression at the point where the 

 afferent vessel enters, and then runs to the wall of the 

 contorted portion of the uriniferous tube, around tvJiich it 

 forms a plexus of capillaries, from which veins arise, and 

 after passing through the medullary portion of the kidney 

 by union and reunion, combine to form the renal vein. 

 The tubuli uriniferi in the medullary portion, in their 

 course from the cortical portion to the pelvis, unite two 

 by two (dichotomously),and as this occurs frecjuently, the 

 whole of the tubes opening by one perforation into the 

 pelvis may be represented by a pyramid, the base of which 

 is at the cortical portion, the apex at the pelvis, and in the 

 foetal colt the kidney is lobulated, divided into the ''pyra- 

 mids of MaljngJii," while the same condition obtains per- 

 manently in the ox. The pelvis of the kidney of the horse 

 is a fan-shaped cavity lined by spheroidal epithelium, and 

 around its convex border a ridge extends on to which the 

 uriniferous tubes open. This ridge terminates laterally in 

 cavities termed calyces of the pelvis, while at the hilum the 

 pelvis is continuous with the ureter. This is a musculo- 

 membranous canal extending along the roof of the abdo- 



