i88 THE MICROSCOPE. 



Take a drop of pus, fresh, without adding anything, and you will see 

 ihe wonderful structure in each pus corpuscle with gre-ft ease. 



Prick your fkin on the palmer surface of the thumb, transport the drop 

 on a slide, and cover right away with a thin covering glass, the ed^es of 

 which have been oiled, so as to prevent evaporation of the fluid. In the 

 perfectly fresh blood you will see the structure in each colorless blood corpuscle. 



Add to a drop of fresh blood a small drop of 40 per cent, soiut. of 

 bichromaie of potash; this will within i hour extract the haemoglobin, and you 

 must succeed in seeing the reticular structure in each red blood corpuscle. 



Keep ordinary yeast (Torula cerevisice) for a fortnight in a 30 per cent, 

 solut. of Bichromate of potash, and examine a drop with a good i-io Immers. 

 lens. You cannot fail in seeing the net-work in each oidium. 



Take any protoplasmic body, best epithelium, cartilage, etc., best kept 

 for a (ew weeks in ^ per cent, solution of chromic acid; take any fresh 

 living protoplasm, such, as for instance, an amoeba from an infusion, and 

 you must see what is to be seen with accuracy. If you fail, come to New 

 York to my laboratory, top floor of my residence, and after two hours you 

 may leave for Chicago, with the satisfaction that the net-work in the proto- 

 plasm is plain. About 400 gentlemen have seen it so far in my place. 



Yours truly. 



Dr. C. Hkitzmann, 



37 West 45ih Street. 



On receipt of this, I repeated the experiments as directed. The 

 glasses I have used are a ^ immersion, made by Wales in 1874; 

 a pretty good glass for one made at that time. It has, in my hands 

 with sunlight and a slip of blue glass, gone through Muller's balsam 

 prube plalle without difficulty. I also used a Powell & Ixaland -^ 

 made later in the same year. With this glass I have glimpsed the 

 lines on the dry amphipleura by simple lamp-light, without any sub- 

 stage appliances whatever. In Mr. ToUes' hands, by the use of his 

 traverse lens, it showed the lines on number 20 of the probe platte 

 fully as well as one of his earlier duplex -igS, although, since that 

 time, I have seen the diatom better with one of his later ji^s. I use 

 a stand made by Bulloch, fitted with a Powell & Lealand achromatic 

 condenser. I find that for making out delicate anatomical structures, 

 with the use of high powers, the condenser is indispensable. 



I began my investigation by the study of blood as directed by 

 Dr. Heitzmann. I split off a thin film of mica and oiled the edges. 

 I then pricked my finger with a needle, put a drop of blood on a 

 slide and covered it immediately with the mica. I began the exam- 

 ination with the -^Q. On bringing a white corpuscle into view, I 

 thought, at fir.'st, that I saw the net-work; a number of fine lines ap- 

 peared, crossing the corpuscle in all directions, but the outlines of 

 the red corpuscles in the field were indistinct. The glass had been 

 used in examining objects protected with a thicker cover, and was 



