APPARATUS, MATERIAL, AND REAGENTS. 



631 



Bulbed Tubes. Glass vessels, such as test-tubes, flasks 

 and pipettes, which are used in dealing with liquid media, have 

 already been mentioned under other headings; but bulbed tubes, 

 Pasteur's bulbs, and various other forms are also required for special 

 experiments. 



(L) APPARATUS FOR INCUBATION. 



There are several forms of incubator, each of which has its 

 advocates. They are mostly rectangular chests, with glass walls 

 front and back, or in front 

 only. A cylindrical model 

 is preferred by some. Two 

 only will be described 

 here D'Arsonval's and 

 Babes'. The former admits 

 of very exact regulation of 

 temperature, and the latter 

 is a very practical form for 

 general use. 



D'Arsonval's Incu- 

 bator. The " Etuve 

 D'Arsonval" (Fig. 264) is 

 a very efficient apparatus, 

 and is provided with a heat- 

 regulator, which enables 

 the temperature to be 

 maintained with a mini- 

 mum variation. It consists 

 of a cylindrical copper 

 vessel, with double walls, 

 enclosing a wide interspace 

 for containing a large 

 volume of water. The roof 

 of the water-chamber is 

 oblique, so that the wall 



rises higher on one side than on the other. This admits of the inter- 

 space being completely filled with water. At the highest point is 

 an opening fitted with a perforated caoutchouc stopper, through 

 which a glass tube passes. The mouth of the cylinder itself is 

 horizontal, and is closed by a lid, which is also double-walled to 

 contain water. In the lid are four openings : one serves for filling its 



FIG. 264. D'ARSONVAL'S INCUBATOR. 



