MICRO-ORGANISMS AS PARASITES. 20 



animal be killed soon after infection, the blood is already found to 

 contain numbers of white blood-corpuscles, enclosing one or more 

 of the tubercle bacilli. A wandering cell which has taken up a 

 tubercle bacillus has no such harmless burden as if it had devoured 

 a particle of vermilion or carbon. With the latter load it might 

 travel a long distance, but under the poisonous influence of the 

 bacillus, changes take place in the white corpuscle which soon 

 bring it to a standstill. It increases more and more in size by 

 continuous multiplication of its nuclei, and at length attains the 

 form and size of the well-known giant-cell. Specimens properly 

 prepared show all the intervening stages between simple epithelioid 

 cells, containing only one bacillus, and fully formed multi- 

 nucleated cells containing many bacilli." 



The further fate of the giant-cell varies. When the course of the 

 disease is slow, the number of bacilli enclosed in the cell remains 

 small ; in the most favourable cases the giant-cell remains, and 

 the bacilli die out. But when the course of the disease is rapid 

 the bacilli multiply rapidly, push through the wall of nuclei, and 

 the giant-cell succumbs. The behaviour of the bacilli in the 

 giant-cells is also most curious. The " idea involuntarily arises in 

 the mind," says Koch, " that there is a kind of antagonism 

 between the giant-cell and the parasites it contains. Where one 

 bacillus only is present, we often find the nuclei of a giant cell 

 collected together at one end, and the bacillus generally in the 

 part of the cell free from nuclei, at the furthest point of the 

 unoccupied pole. But when the number of bacilli is increased, 

 their behaviour towards the nuclei becomes more actively hostile. 

 They crowd more and more towards the periphery of the cell, push 

 between the nuclei, and finally break through the wall formed by 

 them. A considerable increase like this in the number of bacilli 

 seems always followed by the degeneration of the giant-cells and 

 their disappearance, leaving only groups of radiating bacilli to show 

 where they once existed." These facts seem to show that the modern 

 treatment of consumption (though begun, perhaps, empirically) rests 

 on a true scientific basis. In the pure, cold air of mountain regions, 

 or in the equally pure air of the open ocean, the consumptive 

 patient has to grapple only with the bacilli contained in his own 

 system ; there are no fresh spores in the atmosphere ready to seize 



