30 



EXPERIMENTAL GENERAL PHYSIOLOGY 



tube at S; disjoin the gas tube at d, and gently draw air through the 

 cell, thus ventilating it and restoring practically the normal condition. 

 Do the cells resume their normal movement? 



(c) How many times may the cells be brought under the influence 

 of the CO 2 and then, by ventilation, be brought to the normal con- 

 dition again? 



Do you see evidence that any of the animals eat green plants? 

 Do you note any of the reproductive changes in any organism? 

 What is the method of locomotion of the forms studied? Do the 

 organisms respond to such mechanical stimuli as a gentle rapping 

 upon the slide with pencil or scalpel? 



FIG. 9 



Paramcecium bursarium. ec, ectoplasm; en, endoplasm; n, nucleus with nucleolus; a, vestibule; 

 o, oral aperture; a, oesophagus; v, vacuoles; /, ingested food. 



-.1. 



(2) With a drop-tube place a drop of saturated salt solution at one 

 edge of the cover. By placing a piece of dry filter paper at the 

 other edge of the cover, the capillary attraction of the paper will 

 draw the salt solution under the cover and thus mix it with the 

 aquarium water. Study the effect of this upon the animal organism 

 present and describe minutely everything observed. 



(3) Place a drop of 50 per cent, alcohol beside the cover-glass and 

 draw it under as described above. Note results as above. 



(4) In a similar way study the effect of iodine, tannic acid, picric 

 acid, and nitrate of silver. 



(5) Take a deep-celled slide; upon the top of the cell invert a clean 

 cover-glass to which is clinging a "hanging drop" taken from an 

 aquarium well stocked with protozoa. The "hanging drop" should 

 be a small one for two reasons: (1) objects within a small hanging 



