I.] THE FROG. 149 



contour line. Look for places where it may- 

 have been separated in preparation. 



yS. Longitudinal miiscidar laye?' ; thin and deeply 

 stained ; seen to consist of the cut ends of 

 close-set cells. 



y. Circular vmscular layer; relatively thicker 

 than /?; cells close-set and parallel with the 

 free surface (cf. § 7. b. /3). 



8. Sitb)]incous layer ; faint and composed of vas- 

 cular connective tissue. Large blood-vessels 

 will be seen ramifying within it. 



€. Mncoiis membrane ; composed of three layers. 

 A muscular layer, forming a thin stratum im- 

 mediately internal to S; a lymphoidal layer, 

 somewhat like the submucous layer, but con- 

 taining numerous rounded or irregular cells 

 (lymphoidal cells) ; the epitheliiwi^ composed 

 of close-set columnar cells (cf. § 2. b.) whose 

 inner ends for the most part stain very deeply. 



c. Compare similar sections across an intestine the 

 blood-vessels of which have been injected with 

 gelatine (see Appendix C). Note the course 

 of the vessels, and especially the relations of 

 their ultimate ramifications^ 



1 7 . The pancreas. 



Preserve small portions in alcohol of increasing 

 strengths ; stain Avith borax-carmine ; imbed and cut 

 transverse sections ; mount in Canada balsam. 



a. Examine under a low power. 



a. 'Yhe gland ; composed of groups of cells (acini) 



