308 LABORATORY GUIDK IN PHYSIOLOGY. 



cm., and one or two centimeters in thickness. Some prefer 

 to use cork boards which come in pieces 10 cm. by 25 

 cm. and V^ cm. in thickness. 



3. The physiological operating case. 



A convenient case, and one which will be sufficient 

 in the simple experiments presented in this book, contains 

 the following instruments : 



1 medium scalpel, 



1 small scalpel with narrow blade, 



1 medium scissors, 



1 microscopic scissors, 



1 medium dissecting forceps, 



1 microscopic forceps, with curved, serrated jaws, 



2 serre fine forceps, with stiff spring and serrated jaws, 

 1 groove director and aneurism needle, 



1 silver probe, 



1 blunt needle, for pithing frogs, 



2 dissecting needles. 



The case may be of leather or leatherette. Such a 

 case may be used nearly as much in the histological as in 

 the physiological laboratory. 



4. Galvanic cells. 



For general use in the physiological laboratory there 

 is probably no galvanic element superior to the Daniell 

 cell (named after Prof. J. F. Daniell, of King's College, 

 London). Much the most convenient and economical 

 size is the quart or liter cell whose porous cup measures 

 5-6 cm. in diameter and 10 to 12 cm. in height. If more 

 current is needed than is furnished by one of these cells it 

 is very easy to join two or more of them into a battery. 



In large laboratories it will be found expedient to de- 

 vote an old table to the galvanic cells. This table should 



