86 PRACTICAL HISTOLOGY. 



HUMAN KIDNEY. 



Examine (L) a similar section of a human kidney, and note especially the normal thickness 

 of the capsule and its delicate and scanty fibres of attachment to the subjacent organ. (Indicate 

 the capsule, pyramids of Ferrein, convoluted tubules, and Malpighian corpuscles in PL XIX., 

 Fig. 2.) 



(H). Select a Malpighian corpuscle. Observe the membrane or capsule of Bowman, con- 

 sisting of an elastic membrana propria, and note the single layer of squamous epithelium 

 lining it. The nuclei are stained, and bulge slightly into the cavity. Outside it there is a 

 small amount of fibrous tissue. Within it note the tuft of blood-vessels, with their nuclei 

 stained, and the capillaries, perhaps, containing yellow blood-corpuscles (PL XIX., Fig. 3). 

 The capillaries are arranged in two or three conical lobules, but do not completely fill the 

 capsule ; the space between the surface of the glomerulus and the capsule depends on the 

 amount and nature of the secretion present in it. Between the capillaries there is a very small 

 amount of connective tissue (chiefly branched connective-tissue cells), which holds them to- 

 gether ; and over them there is a layer ofsquames. The section may pass through the capsule 

 in the plane of the afferent or efferent blood-vessels ; or the narrow neck which connects the 

 cavity of the capsule with a convoluted tubule may be found. 



Select a convoluted tubule (H). Observe them, one divided longitudinally and another 

 transversely, and observe the limiting membrane, and how closely they are packed in the 

 cortex, with very little supporting tissue between them. Study the secretory epithelium lining 

 them, and note that the lumen of the tube is small, that the epithelial cells are ill-defined and 

 have no cell-wall. They contain a spherical nucleus placed near the attached end of the cell, 

 and their protoplasm is always cloudy and granular. The outer part of the protoplasm is 

 often striated ; this is especially the case if the section has been hardened in ammonium 

 chromate. Some tubules may be found with an angular zigzag bend in them ; these are the 

 connecting tubules. {Indicate a convoluted tubule in PL XX., Fig. i .) 



Select a Pyramid of Ferrein (H) Observe the straight tubules, and amongst these the 

 looped tubules of Henle, with their descending limb, which is very narrow and lined by flattened 

 epithelium, with alternately projecting nuclei on either side. They are not unlike capillary 

 blood-vessels, though they have a well-marked basement-membrane. It is difficult to distin- 

 guish the ascending limb, as it is so like a collecting tubule. The descending branch may be 

 traced downwards into the medulla. (Indicate these tubules in PL XX., Fig. I.) 



The Medulla (H). Observe the straight tubules collecting or discharging tubes which 

 open on the apex of the Malpighian pyramid. Observe their columnar or cubical epithelial 

 covering. The cells are well-defined, and contain a well-marked spherical nucleus, imbedded 

 in clear transparent protoplasm. There is a well-marked lumen in the centre of the tubule. 

 Observe the basement-membrane in which the cells are placed, and note the relatively large 

 amount of connective tissue in the medulla compared with the cortex (PL XX., Fig. 2). 



Place unstained sections of a kidney in a quarter per cent, osmic acid for twenty-four 

 hours, and mount them in Farrant's solution. 



ISOLATED RENAL TUBULES. 



PREPARATION. The arrangement and relation of these parts one to another cannot be 

 made out in a section ; to do so the kidney must be boiled for a long time in a mixture 

 of alcohol and hydrochloric acid, which dissolves the connective tissue and liberates the 

 tubules. A very good method is to place, pieces of a kidney, about the size of a pea, in 



