BLOOD 197 



(In the forms of corpuscles with round nuclei eccentrically placed, the 

 centrosome is on the side where the protoplasm is most abundant.) 

 The polymorphonuclear leucocytes are actively amoeboid, and particles 

 readily pass through their superficial layer, but like other forms of leuco- 

 cytes they are covered with a very delicate cell membrane. 



Max Schultze in the first paper published in the Archiv fur mikroskopische Anato- 

 mic (1865, vol. i, pp. 1-42) described an apparatus for the examination of microscopic 

 specimens at the body temperature, which he used in studying human blood. He ob- 

 served the active creeping movements of the leucocytes, closely similar to those of the 

 most delicate amoebae, and watched them take up particles of carmine and other dyes 

 placed in a drop of fresh blood. "The act of ingestion," as he describes it, "is accom- 

 panied by no striking maneuver." He adds that he has never seen special processes 

 sent out to overcome foreign bodies, but that the creeping corpuscle, during its uniform 

 advance, passes over them and presses them into its substance. He diluted the blood 

 with two-thirds of its volume of fresh cow's milk, and observed that the leucocytes 

 moved with the same rapidity as before, and ingested the oil globules which are much 

 larger than the pulverized dye-stuff. 



A fundamental characteristic of polymorphonuclear leucocytes is the 

 development of distinct granules in their protoplasm. They can be seen 

 in fresh unstained specimens, in which it is evident that some of the cells 

 contain coarse granules, and others fine granules. The lymphocytes 

 and the large mononuclear leucocytes contain neither sort, and are there- 

 fore described as non-granular. In order to study the granules a drop 

 of blood is spread thinly over a cover glass and dried, afterward being 

 stained with a "blood stain," which is a carefully prepared mixture of 

 acid and basic dyes. The details of nuclear structure are not preserved by 

 this method, but the granules are clearly differentiated (Fig. 187). With 

 several of the blood stains the fine granules are colored purple or lilac; 

 and the coarse granules are found to be of two sorts, one kind staining 

 red with eosin, and the other blue with the basic dye. Only one sort of 

 granule occurs in a single cell. 



Leucocytes containing coarse blue granules, which often obscure the 

 nucleus, are called mast cells. In order to distinguish between them and 

 the mast cells of connective tissue, which contain similar granules (see 

 Fig. 55, p. 68) those in the blood are often called mast leucocytes. They 

 form only 0.5% of the leucocytes, and in sections special methods are 

 required to demonstrate them. These cells have recently been inter- 

 preted as degenerating forms, but their significance has not been 

 fully established. 



Leucocytes with coarse granules which stain red with eosin, an acid 

 stain, are called eosinophiles (sometimes oxyphiles, or acidophiles). 

 They constitute from 2 to 4% of the leucocytes in the blood. Eosino- 

 philic cells, apparently distinct from those of the blood, occur also in 

 connective tissue, and since their granules are preserved by ordinary 



