PRINCIPLES OF DIGESTION 51 



microscope a little of the sediment from the bottom of the 

 bottle, mounted in water. Draw several groups of the 

 separate elements of this sediment. (These bodies are 

 yeast plants.) 



(Yeast is a one-celled plant that, with- 

 out changing its yeast character, is capa- 

 ble of transforming sugar into carbonic 

 acid gas arid alcohol. In its power to 

 change a substance, without itself under- 

 going transformation, it acts like an en- ^ 9 

 zyme and hence is called a ferment organ- FlG 2 ^ Yeast Plants: 



ism. Many digestive actions are per- 1 > a P lant 



c bud; 2, the bud near- 



IOrmed either by enzymes or by ferment i y ready to separate 



organisms, with results like that noted in as a new plant - 



Ex. XXX. Most enzymes are produced in the body by 

 organs called glands.) 



XXXII. STRUCTURE OF A TYPICAL GLAND. 



Apparatus. Microscope and accessories used in the study of tis- 

 sues, prepared slide of crypt of Lieb- 

 erkiihn from the small intestine of man. 

 (Any other gland preparation will I 

 serve.) 



Directions. Examine first with 

 the low power. Draw the entire 

 gland and note the following points : 

 the kind of tissue, the arrangement 



Of the Cells, the gland lumen, Or FIG. 25. A Salivary Gland: a, 

 i A TTT- j_i J.T T_ l~ lumen of a gland in longitudi- 



central cavity. With the high nal section; b> a gland in cross 

 power examine a few of the cells section ' c < connective tissue. 

 and their contents. Draw and note the position of 



