1899] MICROSCOPICAL JOURNAL. 63 



place in the inflamed mesentery of a frog" ; was struck by 

 the chang-es in the circulation ; observed the dilatation of 

 the blood vessels, the inital acceleration of the blood fol- 

 lowed by its slowing- up, the mural implantation of the 

 leucocytes in the veins and capillaries, the transmigration 

 (or diapedesis) of the leucocytes. He looked upon the 

 vascular system as the prime factor, and thought that a 

 molecular change in the vessel-walls was the chief cause of 

 inflamation. The adhesion of the white corpuscles (leuco- 

 cytes) to the venous and capillary walls was explained by a 

 g-reater adhesion, a sort of sticky condition : the slowing- up 

 of the current made the lig-hter leucocytes cong-reg-ate at 

 the walls, while the specifically heavier red corpuscles con- 

 tinued to swim in the middle ; through a molecular change 

 in the formerly impervious walls, they became able to 

 let not only a g-reater amount of plasma transude, but 

 also to allow the formed elements to go through by a 

 peculiar process, and without making- a hole in the ves- 

 sel wall. Metschnikoff began to study the lower organ- 

 isms as subjects of irritation. He went down to the very 

 lowest organisms that we recognize as animal, and began 

 with the ameba. 



This is the most simply built of all animals ; it consists 

 in fact of one single cell, a mere mass of living- protoplasm, 

 with a nucleus, and without even an enveloping- membrane. 

 If an ameba is cut in two, the part that retains the nucleus 

 regenerates itself and the lost part g-rows out. If the 

 ameba meets a bacterium, it throws out jelly-like prolong-- 

 ations, that embrace the enemy and gradually coalesce 

 with the mass of the animal, whereby the bacterium soon 

 finds itself enclosed within the ameba ; a contest beg-ins, in 

 which the bacterium by its toxines, secreted by its meta- 

 bolism, impairs the vital functions of the host. If this is 

 strong enough to resist action of the toxines the ameba 

 disintegrates the bacterium, in the cell substance of 

 which we see small g-ranular masses, that finally fall apart, 

 and the bacterium is destroyed ; its remnants are then 

 gradually expelled, and the ameba g-oes on living. If, on 

 the other hand, the bacterium prevails, the ameba dies un- 



