78 BLOOD 



shaped. This is the largest of the several types of leucocyte : 

 they form 2 to 4 per cent of the white corpuscles of the blood. 



3. Polynuclear neutropMle leucocytes (" polymorphonuclear " 

 neutrophiles, polynuclear leucocytes) possess a broad rim of cyto- 

 plasm, which contains fine neutrophile granules, and a deeply 

 staining polymorphous nucleus consisting frequently of three or 

 four ovoid lobes united by a delicate chromatin thread. These 

 are relatively large cells : they form 70 to 72 per cent of the white 

 blood cells, and are therefore the most abundant of the several 

 types of leucocyte. 



4. Eosinophile leucocytes (polynuclear eosinophiles, acidophiles, 

 or oxyphiles) have a broad rim of cytoplasm with very coarse, 

 highly acidophile granules, and a highly chromatic polymorphous 

 nucleus which resembles that of the neutrophiles and consists 

 usually of several distinct lobes united by chromatin threads. In 

 relative size they are similar to the neutrophiles. Eosinophile 

 cells form 2 to 4 per cent of the white blood corpuscles. 



5. Basophile leucocytes (" mast-cells ") are provided with a con- 

 siderable cytoplasmic rim containing coarse basophile granules; 

 they may be either mono- or polynuclear, the nucleus in either 

 case not being richly supplied with chromatin. In size these 

 cells resemble the neutrophiles. They are the least frequent of 

 the several types of leucocytes, but form at least 0.5 per cent of 

 the white blood cells. 



Development of the White Blood Cell.^-The primary origin of 

 the embryonic white blood cells is still a matter of some obscurity. 

 They make their appearance considerably later in fetal life than the 

 red blood cells. According to Saxer,* the first white blood cells are 

 derived by reproduction and differentiation of those same ances- 

 tral mesoblastic cells which at first form only red blood cells, but 

 later the white cells as well. These primitive wandering cells 

 gain admission to the blood vessels by their amoeboid activity. 

 Kostianecki,* however, thinks that these ancestral cells are formed 

 within the dilated portions of the primitive vessels,, and that the 

 earliest white blood cells are therefore formed within the vessel 

 and probably stand in intimate genetic relation with the primitive 

 endothelium.f 



*Anat. Hefte, 1896. 



f The recent studies of Beard have thrown some doubt upon the former 

 conception. This observer finds that there are no leucocytes in the blood prior 

 to the appearance of the anlage of the thymus. He also finds that in the earliest 



