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 and alcohol. In its power to 

 change a substance, without itself under- 

 going transformation, it acts Uke an en- 

 zyme and hence is called a ferment organ- 

 ism. Many digestive actions are per- 

 formed either by enzymes or by ferment 

 organisms, with results like that noted in 

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

 organs called glands,) 



Fig. 24.— Yeast Plants: 

 1 , a plant forming a 

 bud; 2, the bud near- 

 ly ready to separate 

 as a new plant. 



XXXII. — Structure of a Typical Gland. 



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

 sues, prepared slide of crypt of Lieb- 

 erklihn from the small intestine of man. 

 (Any other gland preparation will l- 

 serve.) ^^^l^^iM^^S^E^^j^fJ^-c 



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 Sallvary Oland: a, 



central cavity. With the high 'Z^^^f^'^t:^ 



power examine a few of the cells section; c, connective tissue. 



and their contents. Draw and note the position of 



