MAMMALIAN ANATOMY 
116 
staining of granules in the cytoplasm which otherwise does not 
take up the stain, are as follows: 
Neutrophiles. —In these the nucleus takes a purple stain. 
The granules in the cytoplasm are so fine as to be hardly distin¬ 
guishable as separate granules, so that the reddish-purple stain 
which they take (showing them to be neutral rather than either 
acid or basic in their affinities) seems to impart its color to the 
whole cytoplasm. These are the most abundant of all the types of 
leucocytes, constituting normally 60% to 70% of all the leucocytes. 
Acidophiles or Eosinophiles. —These are characterized by the 
affinity for acids of the coarse granules in the cytoplasm. These 
granules in consequence take on a red color from the eosin and 
are thus conspicuous in an otherwise unstained cytoplasm which 
surrounds the purple nucleus. The acidophiles constitute only 
from 1% to 4% of the total number of leucocytes in normal blood, 
and are thus very difficult to find. 
Basophiles. —In these the nucleus stains only faintly and is 
thus inconspicuous. The coarse granules in the cytoplasm have a 
strong basic affinity and thus stain deeply with methylene blue 
while they may also take on a purplish tinge similar to that 
imparted to the fine granules in the cytoplasm. The blue-stained, 
coarse granules are, however, so conspicuous that they seem even 
to stand out from the surface of the cytoplasm. This is the least 
abundant variety of leucocytes, since they constitute less than 
1% of the whole number. They are therefore seldom seen in a 
single preparation. 
Identify as many varieties as you are able to find and draw 
each variety identified. 
3. The Blood Count by Means of the Haematocytometer.— 
Using the mount of human blood set up for this purpose, make 
the count of erythrocytes as directed by the method accompany¬ 
ing the apparatus, and compute from this the number of erythro¬ 
cytes in 1 cu. mm. of blood. Record the entire computation. 
B. GENERAL PROPERTIES OF BLOOD. 
1. Coagulation. 
Take a quantity (50 c.c. or more) of freshly drawn blood, 
which, if obtained from the abattoir, must be kept at a low tern- 
