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- 

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

 ism. Many digestive actions are per- * a P lant f rmiQ g * 



bud; 2, the bud near- 



formed 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 

 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 SaUvary Gland: a, 



central cavity. With the high ^* +? 



pOWer examine a few Of the Cells section; c, connective tissue. 



and their contents. Draw and note the position of 



