240 SUiVhMAUY OF CURRENT RESEARCHES RELATING TO 



with a sjriiis^e from the patient's vein and add, at once, to the citrate 

 solution in the tube. Mix by revolving or shaking the tube. The 

 blood may be examined at once or at any time during the following 

 twenty-four hours. The dextrose seems to preserve the cells and 

 Plasmodia against changes, and could just as well be omitted if 

 examination was always made within an hour or two after the blood 

 was drawn. Place equal quantities of the citrate-dextrose blood in 

 two large centrifuge tubes— the depth of the column may vary from 

 2-5 c.cm. The length of time for centrifugalization depends upon the 

 length of the arm and the speed of tlie centrifuge. In the authors' case 

 the distance from the centre of the centrifuge to the bottom of the tube 

 was 18 c.cm., necessitating a speed of 2.500 revolutions per minute. The 

 mixture should be centrifuged one minute for each cm. of the column of 

 l)lood to be centrifuged. All the plasmodia (except the small astivo- 

 autumnal riiigs) and the leucocytes, rise to the top of the cell-sediment 

 and are in the lirst O'l cm. With a large pipette skim off as much 

 as possible of this layer from each tube and place in one (or two) 

 5 cm. tubes Take up at the same time as much plasma as cells, and 

 after placing in the small tube mix thoroughly by drawing l)ack and 

 forth into the pipette. The column in the small tube must not be 

 deeper than .") c.cm. Centrifuge as before. Now, with a large capillary, 

 di'aw not more than a 5 c.cm. column of the cells into it from the surface 

 of the cell-column. It is a good idea to mix this bv forcinc: it in and out 

 of the pipette against the surface of a slide. Draw it up into the 

 pipette past the tip and seal the end of the pipette in a flame. Cut off 

 part of the capillary containing the blood and centrifuge as before. 

 After centrifuging, there will be found a small amount of greyish 

 leucocyte mass merging into the column of red cells. In very heavy 

 infections the lower part of the leucocyte layer and the upper part of 

 the erythrocyte column have a brownish appearance from the pigment 

 present in the large amount of plasmodia here. Cut the capillary at a 

 point • 1-0 • 2 cm. below the bottom of the leucocyte layer, and with a 

 smaller capillary draw out the small amoimtof erythrocytes and leuco- 

 cytes and a little plasma to dilute them with. Mix and make one or 

 more blood-spreads of the usual kind. Stain and examine in the usual 

 manner. 



Histological Basis of the different Shank Colours in the 

 Domestic Fowl.* — H. R. Barrows tixed the material in 10 p.c. formalin. 

 Free-hand sections were made and mounted in glycerin. Many 

 fixatives and stains were tried, the best being formalin htematoxyUn. 

 eosin and Sudan iii. The following summary of the results is given : 

 1. Yellow and variations are due to the presence of lipochrome pig- 

 ment in the epidermis witli the absence of melonin pigment. 2. White 

 results from the lack of pigment. '6. Blue colour obtains when melanin 

 pigment lies in the upper dermis, with the absence of this tyi^e of 

 pigment in the epidermis. 4. Black and variations depend upon the 

 presence of melanin pigment in the epidermis. 5. Green appears when 

 lipochrome pigment lies in the epidermis and melanin pigment in the 



* Rep. 'Slaine Agric. Expcr. Stat., 1914, pp. 237-52 (12 figs.). 



