210 APPENDIX. 



mains normal and affords a valuable means of comparison. It 

 is not worth while to make many chemical tests of proteids at 

 this point. 



(b) Carbohydrates. A useful demonstration may be made 

 of various starches, sugars, and glycogen. The iodine-test may 

 be applied if desired. If time allows, the microscopical appear- 

 ance of potato-starch, corn-starch, Bermuda arrowroot, etc., 

 may be dwelt upon in the laboratory-work. Cellulose is well 

 shown in filter-paper or absorbent cotton. 



(c) Fats. A demonstration of animal fats and vegetable oils 

 may be made if tune allows. They may be examined microscop- 

 ically in a drop of milk, in an artificial emulsion made by shak- 

 ing up sweet oil in dilute white-of-egg, or in fresh fatty tissue 

 (from subcutaneous tissue of mouse, or fat-bodies of frog). It is 

 hardly worth while to examine these substances chemically, but 

 a few simple tests may be applied if desired. 



Dialysis. A demonstration of dialysis is easily made by in- 

 verting a broken test-tube, tying the membrane over the flaring 

 end, filling the tube to a marked point with strong salt or glu- 

 cose solution, and immersing it in a beaker of distilled water. 

 After an hour or so the fluid will be found to have risen in the 

 test-tube against gravity. 



Temperature and Protoplasm. The profound influence of 

 temperature on protoplasm is well shown by the frog's heart. 

 Decapitate a frog and destroy the spinal cord. Expose the 

 heart and count the beats at the room temperature. Then pour 

 upon the heart iced normal salt solution. Again count the beats. 

 Next pour upon it normal salt solution heated to 35 C. The 

 nmnber of beats will follow the fall and rise of temperature. 



CHAPTERS IV TO VIII. (THE EARTHWORM.) 



Large earthworms must he used or satisfactory results can- 

 not be expected. Pains should therefore be taken to procure 

 the large L. terrestris (not the common Allolobophora mucosd), 

 which is readily recognizable by the flattened posterior end. 

 This species is not everywhere common ; hence a supply should 

 be procured and kept in a cool place in barrels half full of earth, 

 on the surface of which is placed a quantity of moss. They will 



