200 PRACTICAL HISTOLOGY [XXV 



partially separated in dilute glycerine on a slide ; portions of 

 tubes only are thus obtained. Or the piece is placed in 35 p.c. 

 potassium hydrate for half-an-hour. 



Staining outlines of the epithelial cells. (Demons. 2.) A 

 kidney is cut across, washed with sodium sulphate '75 p.c. : 

 5 p.c. nitrate of silver is poured on it, left for five minutes, the 

 surface is then washed, and exposed to light in water ; when it is 

 brown, sections are made from the superficial layer by the 

 freezing method. 



Injection from ureters. A 2 p.c. Prussian blue solution is 

 allowed to run into the ureter of a dog (anaesthetized and bled) at 

 a pressure of 30 to 40 mm. Hg for a quarter to half an hour, 

 Pieces of the kidney are hardened in alcohol, and cut in paraffin. 



Excretion of sodium sulphindigotate. The method is the 

 same as that for obtaining the bile ducts filled with sodium 

 sulphindigotate (cp. p. 185) except that the spinal cord is cut in 

 the upper thoracic region before the injection. 



Haemoglobin menisci in the capsules. The upper thoracic cord 

 is cut in an anaesthetized dog ; 20 to 30 c.c. of blood is allowed 

 to run from the carotid into an equal volume of water ; this is 

 defibrinated, filtered, and injected at intervals into a vein. In 

 one to two hours the kidneys are cut up and (a) put into boiling 

 water for two or three minutes, (6) preserved in one of the fluids 

 which fixes haemoglobin. 



Glomeruli of frog's kidney injected with silver nitrate. The 

 method of injecting the vessels given on p. 136 may be modified 

 thus. The blood is washed out, the aorta below the kidneys is 

 ligatured and the vena cava inferior clamped ; nitrate of silver 

 *2 p.c. is injected until whitish spots appear on the kidney ; in 

 4 or 5 minutes the vena cava clamp is taken off and distilled 

 water is injected to wash out the silver solution. Then (a) the 

 kidney is mounted whole in balsam ; the stain should be almost 

 confined to the afferent and efferent glomerular vessels and the 

 epithelium of the capsules. (6) The vena cava is again clamped 

 and alcohol or formol injected to fix the glomeruli in a 



