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ROBERT CHAMBERS. 



one must have in which to manipulate the needles. For routine 

 work it may be well to have a chamber of fairly large dimensions 

 disregarding the condenser as it is surprising how much illumina- 

 tion a condenser will give beyond its focal distance. However, 

 for critical work, it is imperative to have the height of the cham- 

 ber such that the objects on the undersurface of the coverslip be 

 close to the focus of the condenser. My condenser has a working 

 focal distance of almost 9 mm. and the chambers I use are 45 

 mm. long, 22 mm. wide and 9 mm. high. 



The moist chamber is lined on the sides with blotting paper 

 leading from the trough to carry the water along the length of 

 the chamber so as to furnish a large moist surface. The liquid 

 in the trough and the blotting paper should be isosmotic with 

 the liquid used for the hanging drop so that evaporation be 

 equalized and the hanging drop not become diluted. 



FIG. 4. Moist chamber for preliminary teasing of tissue. 



For the dissection of the cellular elements of somatic tissues, 

 it is necessary to do some preliminary teasing under an ordinary 

 dissecting microscope. This should be done in a moist chamber 

 of some kind. The tissue is teased on a coverslip which is then 

 inverted and placed on the microdissection moist chamber. 



A handy moist chamber (Fig. 4) can be made out of a shallow 

 box with dimensions approximately 7X5X3 cm., with a top and 

 bottom of glass and the two longer sides of thin rubber sheeting. 

 The coverslip with the tissue to be teased is placed within the 

 box and the teasing is carried out with needles projecting through 

 the rubber sheeting. For the tissue of warm-blooded, animals 

 both the preliminary teasing and the microdissection should, of 

 course, be carried on in warm boxes. 



