TEERMorAXIH OF LEUCOCYTES 261 



local and general increase in eosinophiles, and we may even have 

 local mast-cell leucocj'tosis.^^ 



Tissue cells were found by Adler to migrate far into blocks of elder 

 pith, apparently ratlier later than the leucoc^^tes. As they showed 

 changes of form indicating ameboid motions he considers their migra- 

 tion to be an active process. The existence of the polymorphonuclear 

 forms in the pith seems to be very transient. 



The position taken by the yonng blood-vessels and cells in granula- 

 tion tissue, at right angles to the surface, possibly also depends on 

 chemotaxis determining the direction in which the new cells shall pro- 

 liferate. 



Thermotaxis of Leucocytes. — Heat seems to affect leucocytes 

 much as it does ameba*, moderate temperatures being positively ther- 

 motactic. ^Mendelssohn ^- states that the thermotaxis is most pro- 

 nounced at a temperature of 36°-39° C. (97°-102° F.), but is still 

 marked as low as 20° C. Temperatures higher than 39° C. (102° F.) 

 do not seem to attract them. Wlassow and Sepp ^^ state that motility 

 of leucocytes is increased by warming to 40° C, and that temperature 

 of ■i2°-46° C. causes the movements to become very irregular, with 

 feeble power of contraction. Lymphocytes are not motile at ordinary 

 temperature, but at 44° they begin to move, and once motile, they 

 continue their motion when cooled as low as 35° ; this motility is con- 

 sidered to be entirely abnormal and only the result of degenerative 

 changes. If mixtures of leucocytes and bacteria sensitized with op- 

 sonins are kept at low temperature, the bacteria become attached to 

 the surface of the leucocytes, not being ingested until the mixture is 

 warmed.'^* This indicates that two separate processes are involved in 

 phagoc.ytosis. 



Temperature probably plays but a minor part in attracting leuco- 

 cytes in pathological processes, however. The local heat of an inflamed 

 area is due chiefly to the accumulation of blood in the part, and would 

 not influence the leucocytes to migrate from the still w^armer blood 

 into the tissues. By increasing motility, however, the temperature of 

 fever may favor migration and phagocytosis, and local application of 

 heat to inflamed areas may induce local leucocytic accumulation. In 

 bums the duration of the period of excessive temperature is usually 

 too brief to account for the attraction of leucocytes that results ; this 

 accumulation is undoubtedly due to the products of the resulting cell 

 degenerations. 



31 See Milchener, Zeit. klin. Med., 1809 (37). 194; Massaglia, Cent. f. Path. 

 1910 (21), 534. 



32 Rousskv Vratch, 1903. 

 33Vircho\V's Archiv, 1904 (176), 185. 



34 Ledingham, Proc. Roval Soc, 1908 (80). 188; Sawtchenko, Arch. sci. biol.. 

 1910 (15), 145. 



