Resolution of tlie formed elements 77 



These polynaorpho-nuclear leucocytes are very numerous in the 

 blood and in many exudations and are distinguished by the greater 

 selective affinity of their nucleus for basic aniline dyes and by 

 a certain tendency of the protoplasm to become stained by acid 

 aniline colours, such as eosin. The true macrophages are without 

 granulations, but the " polymorpho-nuclear " leucocytes contain 

 many. These granulations are sometimes " eosinophile," "pseudo- 

 eosinophile" (or " amphophile ") or even " neutrophile " (as in man 

 and the horse). 



These two main groups of leucocytes are generally distributed in 

 the Vertebrate, ; and we already meet with them in one of the lowest 

 vertebrate forms the Ammocoetes (the larva of the lamprey). The 

 macrophages of this fish present all the principal characters of the %~ 

 group to which they belong (protoplasm without granules, easily 

 stained with methylene blue, large nucleus rich in nuclear juice). In [S3] 

 the "polynuclear" forms in this lower vertebrate the protoplasm does 

 not stain with methylene blue, but assumes a faint rosy tint with 

 eosin ; the single nucleus is divided into several lobes. In Vertebrates 

 which are much higher in the scale these characters change. Thus in 

 the cayman (Alligator mississipiemis), according to the researches of 

 Madame Podwyssotsky, carried out in my laboratory, the two great 

 varieties of leucocytes are readily found in the blood, lymph and exu- 

 dations. The macrophages, however, especially in the exudations, are 

 very often furnished with two or several nuclei, whilst the small leuco- 

 cytes possess only a single nucleus, which is not divided into lobes. In 

 spite of this peculiarity the two groups are readily distinguished. The 

 staining reactions of the macrophages are identical with those of the 

 corresponding corpuscles in all the other Vertebrata ; whilst the small 

 leucocytes, in spite of the absence of a polymorphous nucleus, are easily 

 recognised by their eosiuophile granulations and by the special affinity 

 of the nucleus for basic aniline dyes. Under these circumstances it 

 would be quite inappropriate to designate those leucocytes, which are 

 really polynuclear, that is to say, possessing two or several nuclei, by 

 the name of " mononuclear," and to reserve the name of "poly- 

 nuclear " for the small corpuscles which possess only a single nucleus 

 undivided into lobes. For this reason it is much more rational to 

 retain for these so-called polynuclear cells my proposed name of 

 microphages. Moreover, the microphages are true phagocytes. It 

 was formerly thought that the eosinophile leucocytes, such as the 

 " * overfed ' cells (Mastzellen) " of Ehrlich, which are identical with 



