192 



PHO TO-MICROGRAPHY. 



\CH. VIII. 



niteness may he readily obtained. Stained microbes also furnish favorable objects 

 when mounted as cover ^lass preparations. 



Preparations in animal histology must approximate as nearly as possible to the 

 conditions more easily obtained with vegetable preparations. That is, they must 

 be made so thin and be so prepared that the cell outlines will have something of 

 the defiuiteness of vegetable tissue. It is useless to expect to get a clear photo- 

 graph of a section in which the details are seen with difficulty when studying it 

 under the microscope in the ordinary way. 



Many sections which are unsatisfactory as wholes, may nevertheless have parts 

 in which the structural details show with satisfactory clearness. In such a case the 

 part of the section showing details satisfactorily should be surrounded by a delicate 

 ring by means of a marker (see Figs. 61-66). If one's preparations have been 

 carefully studied and the special points in them thus indicated, they will be found 

 far more valuable both for ordimry demonstration and for photography. Tlie 

 amount of time saved by marking one's specimens can hardly be overestimated. 

 The most satisfactory material for making the rings is shellac colored with an alco- 

 holic solution of one of the anilins, blue or green, then in studying the prepara- 

 tion one can see it even where covered by the ring. 



Fig. 147. Walmslefs .Infograph Photo micrographic Camera in a horizontal 

 position. A microscope lamp and bull's-eye condenser are in position. Compare 

 Fig. 148 in (Proc. Amer. Micr. Soc, Vol. XVII, 1893). 



y. o33- 



Light. — The strongest available light is sunlight. That has the defect of 

 not always being available, and of differing greatly in intensity from hour to hour, 

 day to day and season to season. The sun dots not shine in the evening when 



