"Variations in chemiotaxis towards different organisms probably depend in natural conditions, as well as in active immunity, upon the opsonic content of the serum."
"As regards the former, leucocytes are guided chiefly by chemiotaxis, _i. e._ by sensitiveness to chemical substances in their surroundings -- a property which is not peculiar to them but is possessed by various unicellular organisms, including motile bacteria."
"Then as regards natural powers of destroying bacteria, phagocytosis aided by chemiotaxis plays a part, and it can be understood that an animal whose phagocytes are attracted by a particular bacterium will have an advantage over one in which this action is absent."