254 INFLAMMATION, REGENERATION, GROWTH 



under "Edema," Chap, xii) of which the most important seem to be: 

 (1) injury to the capiHary M'alls, produced largely by the chemical 

 causes or products of the inflammation-. (2) increased osmotic pres- 

 sure in the tissues, due to increased or abnormal formation of crystal- 

 ioidal substances with high osmotic pressure from large molecular 

 compounds, many of which are colloids (proteins) without apprecia- 

 ble osmotic pressure; (3) alterations in the hydration capacity of the 

 colloids, whereby, tlirough decrease in salts or increase in acidity, 

 thej^ come to possess a greater affinity for w^ater (^I. H. Fischer). 

 By far the most characteristic feature of inflammation, however, is 

 the hehavior of the leucocytes — their increase in number in the blood, 

 their migration from the vessels and accumulation about the point 

 of injury, and their engulfing and destroying various solid particles, 

 such as bacteria and degenerating tissue elements. These processes, 

 which seem to indicate something approaching independent volition 

 on the part of the leucocytes, may, however, be well explained by ap- 

 plication of known laws of chemistrv' and physics, without passing 

 into the realms of the metaphysical. This will be attempted under 

 the heading of : 



AMEBOID MOTION AND PHAGOCYTOSIS 



The accumulation of leucocytes at a given point in the body indi- 

 cates that some means of communication must exist between this 

 point and the leucocytes in the circulating blood. No direct com- 

 munication by the nervous system or other stnictural method existing, 

 the only possible explanation is that the connnunication is through 

 the fluids of the body, and depends upon changes in their chemical 

 composition or physical condition. As the latter generally depends 

 upon the former, the communication is considered to be accomplished 

 by chemical agencies, and called chemotaxis. 



CHEMOTAXIS 



Changes in the chemical composition of a fluid have been shown 

 frequently to aflPect the motion of living organisms suspended in it. 

 One of the earliest observations was that of Engelmann,^ who no- 

 ticed that Bacterium termo suspended in water tended to accumulate 

 about a bubble of oxj^gen in the water. Pfeffer * discovered that the 

 spermatozoids of certain ferns were attracted powerfully by veiy dilute 

 solutions of malic acid, which is contained in the female sperm cell, 

 indicating that the migration of the sperm cells in the proper direc- 

 tion depends on a chemical communication, and he proposed the term 

 chemotaxis for this phenomenon. Strong solutions of malic acid, on 

 the other hand, repelled spermatozoids. Cane-sugar was found to at- 



3 Botanisoho Zoitiinp, ISSl (.30). 441. 



♦Untersuoh. aiis dem Bot. Institut in Tiiliiii;:(>n, 1SS1-1SSS. Bd. 1 und 2. 



