234 PRACTICAL HISTOLOGY. 



of the vapor which is driven off by the boiling becomes 

 condensed, and flows down again into the flask. After 

 the time mentioned the slices are removed and placed in 

 water; and, after lying in this for a few days, minute 

 shreds, comprising the whole depth from external surface 

 to papillae, are split off' with needles, placed on a slide, 

 and unravelled as much as possible by aid of the dissect- 

 ing microscope. The preparation is covered with a spe- 

 cially large piece of covering-glass (a hair being first 

 added to avert the pressure of the glass on the soft 

 tubules), and stained by drawing picric acid solution 

 under the cover-glass. This soon colors the tissue in- 

 tensely yellow; glycerine may then be allowed to pass in 

 at the border in order to complete the preparation. Some 

 of the tubules will be found isolated for a considerable 

 part of their length, and the passage of the convoluted 

 tubules into the looped tubes of Henle may especially be 

 well seen. The epithelium of the tubules is for the most 

 part well preserved, but that of the convoluted ones has 

 become very granular, and so swollen out as to completely 

 fill up the tubules. 



Preparation 9. Examination of the fresh 

 kidney. When by these various means sufficient 

 acquaintance ha*s been gained with the various 

 tubules and their contents in situ, the examination 

 of the fresh tissue in serum may be attempted. 

 With this object small snips are to be made from 

 different parts of a freshly-cut surface with a pair of 

 curved scissors, and teased out in a drop of serum, 

 with the aid of the dissecting microscope, so as to 

 separate as many of the tubules as possible. In 

 doing this much of the epithelium will become 

 detached, and the characters of the individual cells 

 in the fresh condition may be studied. 



Preparation 10. The epitheloid cells of the capsules 

 of Bowman and of the basement membranes of the tubules 

 may be shown by nitrate of silver. For this purpose a 

 fresh kidney is sliced in half by a single cut with a sharp 

 razor in the direction of the tubules. One of the halves 

 is thoroughly washed with distilled water, and solution 

 of nitrate of silver (one-half per cent.) is poured over the 



