1;.>2 THE BLOOD OF KQUINES. 



results were always obtained. The leucocyte count of jugular 

 blood always increases during exercise, sometimes by over three 

 thousand, whereas after exercise this hyperleucocytosis rapidly 

 decreases, often giving rise to a hypoleucocytosis of short duration. 



Leucocyte counts made from ear and jugular blood showed 

 •the interesting fact that the figure for the former is generally 

 lower than that for the latter — the very reverse of what was 

 found for erythrocytes. In tlie earlier work blood had always 

 been obtained from the ear by making a large puncture, through 

 which blood came freely without application of pressure. Small 

 punctures were now made — so small that without pressure no 

 blood flowed from the wound. The ear was then squeezed at the 

 site of puncture, or at the base, and the blood so obtained 

 subjected to count. The following figures were obtained : — 



Blood obtained from ear by: — Leucocyte count. 



(1) Small puncture and apical pressure 14"3 thousand 



(2) Small puncture and basal pressure 7'4 ,, 



(3) Large jDuncture and no pressure ll'B ,, 



Jugular blood for comparison 12'4 ,, 



These data demonstrate the tendency of the leucocytes to 

 cling to surfaces, and this explains all the observed facts. That 

 is, the increase in the number of leucocytes in jugular blood with 

 exercise, and why the number in ear blood is generally lower than 

 in jugular blood. 



The microscopic characters of the leucocytes are brought out 

 by staining blood films in certain ways, especially well by using 

 Giemsa's stain. In films so stained at least five morphologically 

 different leucocytes can be seen. These are conventionally named 

 lymphocytes, monocytes, neutrophiles, eosinophiles and baso- 

 philes. By noting the nature of, say, 200 consecutive leucocytes 

 in specially prepared stained films, one obtains the relative pro- 

 portions in which these cells are present in the blood, and these 

 figures, expressed as percentages, constitute the so-called " differ- 

 ential count of the leucocytes." 



Smears eminently suitable for differential counts are made by a 

 simple modification of Ehrlich's method. A small drop of blood 

 is quickly transferred to a slide by means of a suitable platinum 

 loop, and a cover slip, as broad as the slide, immediately lowered 

 over it. The droplet at once spreads as a thin circular layer and 

 on drawing the slip lengthwise over the slide all ths blood is left 

 upon the latter as a thin film in which the distribution of 

 leucocytes is remarkably uniform. Such smears are eminently 

 suitable for differential count after Giemsa staining in the usual 

 way. 



