178 Chapter VII 



dog; these may be found inside epithelial cells. But here these 

 actively motile bacteria make their way into the interior of vacuoles 

 which open on the free surface.. Attracted, probably, by the epi- 

 thelial secretions the spirilla first draw near to the cells and then 

 take advantage of small openings through which they pass into the 

 secretory vacuole. In almost all cases, however, living and even 

 actively motile bacteria are incapable of penetrating into cells. Thus, 

 when we observe the spirilla of recurrent fever or of goose septicaemia 

 in the neighbourhood of leucocytes, we often see them exhibit very 

 brisk corkscrew movements on the surface of these cells without ever 

 being able to invade them. On the other hand, when the leucocyte 

 sends out a process towards the spirillum ingestion rapidly takes 

 place. In anthrax exudations, or in the spleen of animals that have 

 succumbed to anthrax, large numbers of bacilli may often be ob- 

 served in the immediate neighbourhood of the leucocytes or of the 

 cells of the splenic pulp, without a single bacillus being found within 

 these cells. Nor do we ever see any bacteria (which develop 

 abundantly in a drop of exudation withdrawn from the organism) 

 invade the dead leucocytes, lying alongside them. Whilst on the 

 other hand we see the micro-organisms swarming outside the neigh- 

 bouring leucocytes and occupying the free spaces between these 

 cells. 



Almquist 1 has recently described a method by means of which 

 micro-organisms can be taken into the substance of dead leuco- 

 cytes. He collects leucocytes from mammalian blood, mixes them 

 with bacteria, and centrifugalises the mixture for some time. He 

 convinced himself that after a not very prolonged contact the bacteria 

 are found within leucocytes. Here Almquist excluded phagocytosis, 

 properly so-called, that is to say, the ingestion of the bacteria by the 

 active movements of the leucocytes; but he does not give sufficient 

 proof that the cells, in his experiments, were actually dead. He thinks 

 that the relatively low temperature (below 15C.) excluded the 

 possibility of amoeboid movement in the leucocytes of warm-blooded 

 [189] animals. This argument, however, does not accord with actual fact, 

 for it is indisputable and we have often convinced ourselves of this 

 that the leucocytes of man and warm-blooded vertebrates maintained 

 at even a lower temperature than 15 C. are quite capable of motion 

 and of ingesting foreign bodies. In all cases, the data as a whole, some 

 1 Xttchr.f. Hyg., Leipzig, 1899, Bd. xxxr, S. 507. See review by Podwyssotsky 

 ii) the Arch, russes de Path., St Petersb., 1899, t. vin, p. 257. 



