276 OYTOLOGICAL METHODS. 



CHAPTEK XXVI. 



OYTOLOGICAL METHODS. 



598. The Methods of Study. There are three ways of obtain- 

 ing knowledge of cell-structure study of living cells, study 

 of fresh unhardened cells, and study of hardened material in 

 sections. Of these the last is the most fruitful ; and I advise 

 the beginner to keep as close as possible to the method of 

 Flemming and Rabl, utilising unhardened material chiefly for 

 the purpose of controlling the results obtained by the study 

 of sections, and reserving the study of living cells chiefly for 

 establishing the seriation of already observed phenomena. 



599. Observation of Living Cells. One of the best objects 

 for this purpose is the tail of young larvse of Amphibia, both 

 Anura and Urodela. 



In the living animal the epithelial cells and nuclei (in the 

 state of repose) are so transparent as to be invisible in the 

 natural state. They may, however, be brought out by cura- 

 rising the larva; or, still better, by placing the curarised larva 

 for half an hour in 1 per cent, chloride of sodium solution. 

 Normal larvae may be used for the study of the active state 

 of the nucleus, but much time is saved by using curare. 



Curare. Dissolve 1 part of curare in 100 parts water, and 

 add 100 parts of glycerin. Of this mixture add from 5 to 10 

 drops (according to the size of the larva), or even more for 

 large larvae, to a watch-glassful of water. From half to one 

 hour of immersion is necessary for curarisation. The larvao 

 need not be left in the solution until they become quite 

 motionless ; as soon as their movements have become slow they 

 may be taken out and placed on a slide with blotting-paper. 

 If they be replaced in water they return to the normal stntc 

 in eight or ten hours, and may be re-curarised several times. 



Etherisation. Three per cent, alcohol, or 3 per cent, ether, 



