286 



MICROTOMES AND SECTION KNIVES 



\_CH. X 



enough, and a limited number of the parts of higher animals are suitable for 

 microscopic study without mechanical preparation except merely mounting 

 them on a microscopic slide. Usually the parts of animals are so large and so 

 opaque that the histologic elements or cells and their arrangement in organs 

 can only be satisfactorily studied with a microscope after the tissue, organ, 

 etc., have been teased apart with needles, ( 357) or sectioned into thin layers. 



FIG. 225 



FIG. 226 



FIGS. 225-226. Washing apparatus for tissues fixed in osmic and chro- 

 mium mixtures. As shown in the figures the apparatus is connected with the 

 zvater pipe by a small side cock. It is composed of a double vessel, the inner 

 one being made of perforated brass. There are special perforated dishes to 

 insert in the little compartments. For ova and other small objects a piece of 

 gauze is used in the compartment. This apparatus is convenient for washing 

 'cover-glasses, for the washing out for iron hemato.vylin, etc. The deeper box 

 at the right answers for the slide baskets or holders (Fig. 244). 



MICROTOMES AND SECTION KNIVES 



\ 432. The older histologists, those who laid the foundations and whose 

 understanding of the finer structure of the body was in many ways superior to 

 the knowledge possessed by workers at the present time, did their mechanical 



