180 PHAGOCYTOSIS 



have the power of becoming so are actively phagocytic. Endothelial 

 cells of the lymph-spaces and serous cavities are especially active, not 

 only in the phagocytosis of other cells and cellular debris, but also of 

 various bacteria. In exceptional instances epithelial cells may act as 

 phagocytes. In the presence of an irritant these cells may become de- 

 tached and act as phagocytes; this is exemplified in the case of chronic 

 passive congestion of the lungs, in which the alveolar cells of the lung 

 ingest the hemosiderin formed and deposited (heart failure cells). 



Relation of the Cell Types to Infection. The kind of cells that take 

 part in phagocytosis is determined to some extent by the nature of the 

 irritant. Thus in acute pyogenic infections the polynuclear cell is 

 found to be most active. (See Fig. 46.) It is extremely rare to find these 

 cells containing bacilli in the tissues, although they will take them up 

 readily enough under the artificial conditions of an opsonic determina- 

 tion. (See Fig. 53.) In chronic bacterial infection, such as tubercu- 

 losis and syphilis, and in infections with various fungi, the small lympho- 

 cyte and macrophages are the types most concerned. 



Experimental evidence regarding lymphocytic activity is quite con- 

 tradictory. Undoubtedly many of the cells in the lymphocytic accumu- 

 lations seen in such conditions as tuberculosis and syphilis are not really 

 lymphocytes from the blood, but are newly formed cells of the tissues. 

 There is no direct means of inducing experimentally a local accumula- 

 tion of lymphocytes similar to that induced by most any irritant, 

 resulting in an outpouring of polynuclear cells. Long-continued in- 

 toxication of animals may result in increasing the numbers of lympho- 

 cytes, but the local introduction of the toxin leads to an accumulation 

 of polynuclear cells, rather than lymphocytes. Reckzeli l found that 

 in lymphatic leukemia, in which the lymphocytes greatly exceed the 

 polynuclears, the pus from an acute lesion or the fluid from the vesicles 

 produced by cantharides, contained practically no lymphocytes, but 

 was composed of the usual polynuclear cell forms. Wlassow and Sepp 2 

 state that lymphocytes are not capable of ameboid movement or 

 phagocytosis at ordinary body temperature; Wolff, 3 on the other hand, 

 claims that tetanus and diphtheria toxins produce lymphocytosis in 

 experimental animals, and Zieler 4 claims that in the skin of rabbits 

 exposed to the Finsen light active migration of lymphocytes takes place 

 during the reaction. General lymphocytosis may be produced experi- 

 mentally by the injection of pilocarpin and muscarin, but these bear 

 relation to the vital process of phagocytosis, as they are apparently ex- 



1 Zeit. f. klin. Med., 1903, 50, 51. 2 Virchow's Archives, 1904, 176, 185. 

 8 Berl. klin. Woch., 1904, 41, 1273. 4 Central. f. Pathol., 1907, 18, 289. 



