Plate III. Two examples of rat-kidney sections prepared by the freeze- 

 drying method, and then treated by cytochemical techniques. Figure A 

 shows a section treated by the tetrazodianisidine technique, followed by 

 K acid (see Chapter 5). Note the excellent preservation of the mito- 

 chondria and the nuclei, and the fine detail of the free borders of the 

 secretory cells demonstrated in the central tubule (L. G. Bell). Figure B 

 show r s a similar section treated by the glycerophosphate technique for alka- 

 line phosphatase; incubation time, 20 minutes. All the structures in Fig. B 

 appear by virtue of their phosphatase content only. Note that phosphatase, 

 though most abundant in the secretory borders of tubule cells, is evident 

 also in all cell borders of the tubule cells. Note also the uniform distri- 

 bution of phosphatase in the nuclei apart from the nucleoli, which are 

 richer in phosphatase than the remainder of the nucleus. 



