132 



Journal of Applied Microscopy. 



may advantageously be used since this 

 destroys the plasmatic bodies in the cell 

 without injuring the starch bodies. The 

 specimen prepared as above is laid 

 while damp upon a slide and treated 

 until the starch grains turn blue with a 

 mixture of water 15g., iodide of potas- 

 sium 1.5., and iodine 0.05 g. A drop of 

 this iodine solution is usually sufficient 

 for small preparations. The colored pre- 

 paration is then washed with distilled 

 water until the cell membrane and the 

 plasma have lost their iodine color. 

 Then put on one to several drops ac- 

 cording to the size of the preparation, of 

 a solution of silver nitrate and place it 

 in a bright light for a few moments. 



The preparation then becomes white 

 or yellowish white through the preci- 

 pitation of iodide of silver in the starch 

 grains. The iodide of silver may now 

 be reduced by the use of a "developer." 

 This consists of distilled water lOOg., 

 sodium sulphite lOg., hydrochinon 2g. If 

 this developer is used, to each cubic 

 centimeter of the same is added a drop 

 of a ten percent, solution of potassium 

 carbonate. The iodide of silver prepara- 

 tion previously washed out carefully in 

 distilled water is then treated, accord- 

 ing to its size, with one to several drops 

 of this mixture. The preparation now 

 becomes a soft brown. If it has a red- 

 dish brown color, it is washed out with 

 water and mounted in glycerine. In 

 successful preparations the starch 

 grains retain their original form and 

 structure and are colored a beautiful 

 yellowish brown. Cell membranes and 

 protoplasm remain colorless. If they re- 

 tain a yellowish color or if there is a 

 fine, colored precipitate in the cell then 

 the iodine solution has not been washed 

 out with sufficient care. 



The color of starch grains treated as 

 above may be "intensified." To do this 

 the colored specimen is treated until 

 it is white with a solution of Ig. of sub- 

 limate and Ig. of potassium bromide in 

 50cc. of water. 



Then it is very carefully washed out 

 with water and treated with the hydro- 

 chinon developer in the manner men- 

 tioned above. By this method the starch 

 grains are colored a dark brown. 



A reddish brown coloration may be ob- 

 tained by using palladium. The section 

 stained as above in the iodine-potassium 

 iodide solution is well washed with wa- 

 ter, then heated with a solution of palla- 

 dium chloride (Pd. CI. 2) 0.2 gramme in 

 20 grammes of water, and after a few 

 minutes again carefully washed in water. 

 The starch grains then have a beautiful 

 brown color. 



Charles WraGHT Dodge. 



University of Rochester. 



Notes on Microscopical Technique. 



G. Cakl Hubee, M. D. 



Fifth Paper. 



METHODS FOR MICROSCOPIC EXAMINATION 

 OF HUMAN BLOOD. 



The microscopical examination of the 

 blood has in recent years become such 

 an important part of systematic clinical 

 examinations, that many clinicians have 

 resource to it, not only in diseases of 

 the blood and hematopoietic organs, but 

 also in a great variety of other patholo- 

 gical conditions. It seemed advisable, 

 therefore, to draw attention to some of 

 the methods used in such an examina- 

 tion, in the closing article of this series 

 on elementary microscopical technique. 



In doing so, 1 shall follow the plan 

 adopted in the other articles, of treating 

 the subject in a most elementary way, 

 not so much with a view of aiding those 

 who may already have a working knowl- 

 edge of these methods, but rather those 

 not as yet familiar with them. Space 

 does not permit more than a discussion 

 of the methods to be used. For an ac- 

 count of the sti'uctural elements of nor- 

 mal blood, their variation in structure, 

 and relative proposition in pathological 

 conditions, the reader is referred to the 

 special text-books on the subject. 



COUNTING BLOOD CELLS. 



The instrument now generally used for 

 this purpose is the Thoma-Zeiss hae- 

 macytometer. This apparatus consists 

 of two parts, pipettes by means of which 

 the blood is diluted one hundred times, 

 when counting red, or ten times when 

 white blood cells are to be counted; and 

 a glass slide, on which there is a small 

 well of known depth, the bottom of the 

 well being divided off into small squares. 

 The pipette used when counting the red 

 cells consists of a capillary tube, near the 

 middle of which there is an ampullar 

 enlargement. This is so graduated that 

 the cubical contents of the capillary tube 

 are just one-hundredth part of the cubi- 

 cal contents of the ampulla. The blood 

 to be examined is drawn into the capil- 

 lary tube, to a line marked "1" (just be- 

 low the ampulla); the end of the pipette 

 is then inserted into the diluting fluid, 

 and this is sucked up until the diluted 

 blood reaches a line marked "101" (just 

 above the ampulla). The pipette is then 

 carefully shaken to mix thoroughly the 

 blood and the diluting fluid. 



Either of the following two solutions 

 may be used for diluting the blood: 



Hayem's Solution. — Bichloride of mer- 

 cury, 0.5 gram; sodium chloride, 1.0 

 gram; sodium sulphate, 5.0 grams; 

 distilled water, 200.0 cc. 



