IMMUNITY AGAINST MICROBES. 449 



Hesse has arrived at similar results by injecting virulent 

 anthrax into the veins of animals, such as frogs and dogs, 

 which are naturally immune against anthrax. 



lu tuberculosis, also, giant-cells are met with in all tuber- 

 cular tissues ;^ but one may say that whenever the bacilli of 

 tubercle invade the tissues through the blood, giant-cells are 

 met with in the blood-vessels of these regions. When a pure 

 culture of virulent tubercle bacilli is injected into the lateral 

 vein of the ear of a rabbit, the bacilli, becoming arrested in 

 the veins and capillary vessels of the liver and spleen, give rise 

 to small fibrinous coagula, in which they multiply up to the 

 fifth or seventh day. After a week the cells of the spleen and 

 the leucocytes proliferate actively in the vessels, and the 

 colonies of bacilli become surrounded by migrating cells, which 

 develop into epithelioid and giant cells. 



Up to the present time I have only stated the microscopical 

 facts which may be observed under the microscope. I have 

 not attempted to explain why the cells migrate or not out of 

 the vessels. This question will be fully discussed in the next 

 part of the paper, when I intend to speak of the influence 

 exerted on amoeboid cells and on the other anatomical elements 

 of the tissues by the chemical poisons secreted by micro- 

 organisms. 



Note. — In a lecture delivered before the Royal Institution 

 on February 20th, 1891, my friend Dr. E. Klein, F.R.S., 

 vehemently attacked the whole theory of immunity being due 

 to the action of phagocytes. I do not intend to break through 

 the plan of this work in order to answer Dr. Klein's objections, 

 as the facts on which he bases his theories will be fully discussed 

 later on ; but I take this opportunity of saying at once that I 

 fully maintain the truth of every one of the observations 

 which I have made, and every new fact which I have observed 

 lately confirms me in my opinion. 



' Cornil and Babes, ' Les Bacteries,' vol. ii, p. 92. 



VOL. XXXII, PART IV. — NEW SER. H H 



