THE FROG. 151 



to be due to the presence of red corpuscles 

 whose nuclei alone stain with great intensity, 

 the bodies of the corpuscles remaining faint and 

 yellow. 



8. Bile capillaries ; apparent as a system of minute 

 inter-cellular passages. Look for them in your 

 thinnest sections ; their cut ends appear some- 

 times as round or oval spaces, at others as deeply 

 stained dots, between applied cells, much smaller 

 than the nuclei of the same. 



They may often be demonstrated if, prior to 

 removal of the liver from the body, the bile-duct 

 be ligatured and the bile injected into them by 

 gently squeezing the gall-bladder. 



c. Compare sections of injected liver, prepared as 

 directed for the intestine 1 6. c. 



d. Tease up a fragment of fresh liver in salt solution 

 and examine with \ objective. 



a. The hepatic cells ; polygonal and granular, often 

 containing oil-drops (cf. osmic acid reaction). 



/?. Treat with acetic acid : a nucleus, or sometimes 

 two, will be rendered apparent in each of the 

 cells. 



e. Tease up a similar fragment in iodine solution. 

 Many of the cells will be seen to contain a product 

 (glycogeti) which stains a deep reddish brown. 



19. The kidney. 



Preserve a frog's kidney in alcohol of increasing 

 strengths ; stain with haematoxylin or borax-carmine ; 

 imbed it and cut into longitudinal sections parallel 

 with its flat surface. Mount in Canada balsam. 



