STRUCTURE OF THE URINARY TUBULES. 93 



posed is by no means homogeneous, but presents numerous fat 

 drops and other dark granules distributed through its amor- 

 phous substance, that clear away on the addition of diluted acids. 

 These particles occasion a degree of cloudiness that is usually 

 sufficient to conceal the nucleus, unless acid have been pre- 

 viously applied; and this peculiarity has led to the term 

 cloudy epithelium being applied to indicate that which lines 

 the tortuous urinary tubules. 



Fig. 145. Fig. 146. 



Fig. 145. Section through the cortical canals of a fresh kidney, 

 showing the cloudy epithelial layer. The spheroidal nuclei are con- 

 cealed ; in the wider tubules, irregular, in the narrower regular, 

 fissures divide the epithelial mass. 



Fig. 146. An isolated fragment of a small urinary tubule, with fine, 

 clear, delicate epithelium, and with alternate swellings caused by the 

 nuclei. 



The slender portions of the canal (fig. 146) which run to 

 and from the loop of Henle, instead of being lined with this 

 dark and thick epithelium, possess a thin and clear continuous 

 layer which projects considerably at certain points, owing to 

 the presence of nuclei. 



Where on the other side of the loop the diameter of the 

 tubule again increases, the shape of the investing mass of the 

 nucleus is so far altered and peculiar, that a split now begins to 

 make its appearance about half-way between every two nuclei, 

 which is open towards the wall, and pointed towards the bore 

 of the canal. The epithelium in consequence presents the 

 appearance of being composed of clear separate columnar cells, 



