INTRODUCTION. xxix 



Mr. Schdfer's constant temperature apparatus. The following apparatus, devised by Mr. 

 Schafcr, is an excellent one (fig. 13). It consists of a brass box, a, just like a Strieker's 

 warm stage, having a hole in its centre to admit light to the microscope. In it is a ther- 

 mometer, b. This box lies on the stage of the microscope. It is connected by elastic tubes 

 with a hollow jacket,/", and the whole system is filled with water previously boiled to expel 

 the air. The water is warmed at g by a small gas-flame, the size of which is regulated by 

 a modified Bunsen's regulator, d. By means of the screw e the temperature is regulated at 

 starting. 



METHOD OF APPLYING VAPOURS AND GASES. 



A simple apparatus is described at p. 1 1 for applying the vapour of ether or chloroform 

 to an object, e.g. to cilia. It is made in the same way as the moist chamber described at 

 p. xxviii. 



If gases, such as oxygen or carbonic acid, are to be applied, two tubes require to open 



Fig. 14. SECTION OF A GAS CHAMBER, a, Entrance ; b, Exit tube ; c, Object ; 

 if. Cover-glass. Natural size. 



into the glass cell, one for the entrance of the gas, and the other for its exit. Fig. 14 shows 

 a section of such an arrangement. The cover-glass, with the object on it is inverted over the 

 cell. Strieker's warm stage is usually so made that it can be used for this purpose. 



