§ 1] METHODS 221 



the initial temperature being always supposed to be 0°. Far 

 lower temperatures than these have been obtained by phy- 

 sicists, notably Pictet, to whose work we shall refer again 



Fig. 65. — Gobi's stage aquarium. A, the aquarium proper; T, holder for the 

 aquarium; H, B, slides, with springs. (From CoRi, '93.) 



(p. 240). The organisms to be acted upon may be kept in an 

 apparatus (Fig. 66) like that employed by Pottchet ('66). 



Throughout this chapter, as indeed throughout the whole 

 book, thermometric readings are given in Centigrade scale. 



Pig. 66. — Cold chamber seen in external view and in section. The wall is composed 

 of an inner cylinder containing the freezing mixture and the receptacle for the 

 object of experimentation, and an outer cylinder separated from the inner by a 

 packing of fragments of charcoal. The receptacle containing the organism is 

 provided with a thermometer and an air tube. (From Pouchbt, '66.) 



