PLA'i'lO 4 



EXPLANATION OF FIGURES 

 SPIRAL VALVE. POTASSIUM CHROMATE 



14 Normal spiral valve. 



15 Effect on spiral valve of potassium ohromato jjoisoning. Note the loss 

 of iniionnost epithelium. Severe congestion. The entire section is poorly 

 stained, although it was prepared simiharly and stained simultaneously with the 

 section shown in figui-c 14. 



150 



