312 INFECTION AND IMMUNITY 



tions of the organism at large. Further than this the death of leuco- 

 cytes does not matter, as would the death of specialized and nerve- 

 controlled cells, for no special metabolic or functional derangement 

 occurs from their destruction. 



In considering this independence of the leucocytes it must not be 

 assumed that they have not varied from primitive ameboid cells, for un- 

 doubtedly their life and proper functioning are largely determined by the 

 special plasma in which they live, and it may be that their food, although 

 at times crude compared with that of the other body ceUs, is never- 

 theless usually prepared for them by processes going on in the plasma. 



Questions relating to the independence and to the interrelation of 

 the plasma and leucocytes in their action on invading microorganisms 

 and the action of plasma as compared with serum have been ground for 

 scientific strife for many years, one side contending for the activity of 

 the plasma, the other for the activity of the phagocytes ; the humoralist 

 at first neglecting, if not absolutely forgetting, that a fluid can not be 

 self-replenishing, while the supporters of phagocytosis largely over- 

 looked the fact that plasma is not necessarily an inert menstruum such 

 as salt solution. 



While these differences have been to some extent adjusted by the 

 theory and work of Ehrlich, an immediate point of contention is still the 

 question of the similarity of action of plasma and serum. The humoral 

 school contends that the alexin of Buchner — complement of later 

 writers — is secreted into the plasma, while the Metchnikoff school 

 claims that it is only given up from injured leucocytes in the body, 

 and to the serum by destruction of leucocytes during coagulation. The 

 Metchnikoff school admits, however, that the amboceptors necessary 

 for bactericidal and bacteriolytic action are formed in excess in the 

 phagocytes, and given off from these to the plasma, yet asserts that 

 they are inactive for lack of the complement which is normally retained 

 in the leucocytes, and that they simply prepare the bacteria for com- 

 plete digestion in the leucocytes. The relation of the bacteriolytic ambo- 

 ceptors to intracellular digestion is not settled, although it seems illogical 

 for a digestive body to be produced in excess that has not arisen from 

 cells by the stimulation of its use, and, as the leucocytes take up the 

 bacteria, they are the most likely producers and users of this body. 



In 1894 a further adjustment of differences took place, when certain 

 phenomena observed by Denys and his pupil Leclef demonstrated that 

 the act of phagocytosis when performed in serum, in some instances 

 at least, was dependent on the presence of certain substances in the 



