Resorption of the formed elements 79 



very useful, when the exact origin of a large phagocyte is not 

 known, simply to name it " macrophage." 



The two principal groups of phagocytes (1) fixed and free 

 macrophages, (2) microphages are distinguished not only by their 

 morphological characters ; they also give evidence of very marked 

 physiological differences. All phagocytes are endowed with amoeboid 

 movement which allows them either to move about freely or merely 

 to put out protoplasmic processes. These movements are regulated by 

 a very great sensitiveness, often different in the two groups. Besides 

 a tactile sense, the phagocytes possess a kind of sense of taste or 

 chemiotaxis which enables them to distinguish the chemical com- 

 position of the substances with which they come in contact. The [85] 

 existence of this chemiotaxis could be anticipated from the moment 

 that an important part in the life of the organism began to be 

 ascribed to the amoeboid cells. Leber 1 , Massart and Charles Bordet 2 

 have, however, demonstrated it by rigorous experiment. Following 

 the method used by Pfeffer to demonstrate the chemiotaxis of the 

 vegetable spermatozoids and of Bacteria, these investigators intro- 

 duced into the bodies of higher (rabbits and guinea-pigs) and lower 

 (frogs) Vertebrates small glass tubes filled with different solutions 

 (peptone, broth, salts, bacterial products, etc.). The leucocytes, 

 guided by their positive chemiotaxis, made their way into the 

 tubes and there formed plugs which were often very voluminous; 

 when, on the other hand, the chemical composition of the solutions 

 excited their negative chemiotaxis, the leucocytes avoided the tubes. 



Having acquired information as to the chief characters of the 

 leucocytes, we may ask, To which group do those amoeboid cells, 

 which, according to the observations of Langhans and many other 

 investigators, bring about the resorption of the red corpuscles of the 

 blood, belong? This resorption goes on more rapidly and is observed 

 much better if, instead of introducing blood of the same species into 

 any part, we inject defibrinated blood, or red blood corpuscles from 

 which the serum has been removed by washing, from another species 

 of Vertebrate. It will be found best to inject the nucleated red 

 corpuscles of lower Vertebrates into Mammals, or (as already de- 

 scribed above) to introduce the non-nucleated red blood corpuscles 

 of Mammals into lower Vertebrates. In all these cases the injection 



1 Fortschr. d. Med., Berlin, 1888, Bd. vi, & 460; "Die Entstehung der 

 Entziindung," Leipzig, 1891. 



2 Journ. publ. par la Soc. roy. d. Sc. med. et nat. de Bruxelles, 1890, 3 Feb. 



