88 IMMUNOLOGY 



sponsible for the great i:)i"ogress tliat lias been made in our knowl- 

 edge of the phagocytic cells of the body. Some of these important 

 contributions may be listed as follows : 



1. He was probably the first to recognize the distinction between 

 acid and basic dyes. 



2. He used them to differentiate between acidophilic and baso- 

 philic leucocytes. 



3. He prepared what he called "neutral stains" with Avhich he 

 demonstrated the existence of neutrophiles. 



4. He prepared benzidine dyes such as trypan blue and triphenyl 

 methane dyes such as pyrrhol blue and isamine blue that were 

 later used by Bouffard (1906) and Goldmann (1909) in their 

 important works on vital staining and are now employed ex- 

 tensively in experimental hematology. 



5. He prepared neutral red Avhich has been used by Metchnikoff, 

 Sabin and others in supravital studies of amoeboid cells. 



By means of the acid colloidal dyes of Ehrlich, Goldmann (1909) 

 demonstrated the significance of vital staining. In 1913 Aschoff 

 employed lithium carmine, trypan blue, pyrrhol blue, and other 

 dyes in a study of the extensive system of phagocytic cells scattered 

 throughout the body. Purely upon the basis of the capacity of 

 the various cells to take these acid colloidal dyes and store them, he 

 divided the system, which he named reticulo-endothelial, into six 

 groups. In the following arrangement in which the order given by 

 Mann and Higgins is reversed, group one contains tlie most actively 

 pliagocytic cells while tlie cells of group six are almost devoid of 

 phagocytic powers. 



1. The monocytes of the blood (Plates I and II) 



2. Wandering cells of the connective tissue called clasmatocyte 

 by Ranvier, polyblast by Maximow, and macrophage by 

 Metchnikoff (Plate II) 



3. The living cells of the blood sinuses of the spleen, the lymph 

 sinus of the lymph glands, the blood sinuses of the liver, bone 

 marrow, suprarenal cortex, and hypophyses (Plate III) 



4. The reticular cells of the splenic pulp and cords of Ijonph 

 nodes 



f). Fibrocytes 



6. The ordinary endothelial cells of the lymphatic and vascular 

 system 



