62 TBXr-BOOK OF BACTERIOLOGY. 



stains is precisely the opposite of that of all other cells. They are 

 generally found as large, flat formations of the outer walls of the 

 vessels, and consist of a nucleus and a very fine-grained proto- 

 plasm. Now, with these cells it is only the protoplasm that stains; 

 the nucleus remains uncolored and therefore escapes all but a very 

 attentive observation ; the cell body, however, presents an even, 

 deeply-colored heap of granules, which in fact has a very strong 

 resemblance to a colon3' of micrococci. 



Often, indeed, these cells have been taken for such a colony, and 

 more than once they have been taken for the long-squght cause of 

 some particularly interesting disease. From the insignificant cold 

 in the head to the terrible hydrophobia they have, perhaps, for a 

 longer or shorter time, been taken for the source of all the diseases 

 which could be thought to proceed from bacteria, and it is hardly 

 to be expected that they should soon cease to play this deceptive 

 role. 



Their true nature may be recognized without much difficulty by 

 their granules being of unequal size, by the nucleus being generally 

 recognizable when carefully sought, and by there being usually 

 several such cells, of exactly the same size and appearance, to- 

 gether. It is, further, a remarkable fact that these plasma-cells 

 often stain with a different tint from the surrounding tissue. This 

 is most clearly seen when the sections are treated with methyl- 

 blue; as a rule the plasma-cells become deep violet, so that it seems 

 as if a special chemical combination took place between them and 

 the coloring matter. The plasma-cells are also sometimes accessi- 

 ble to Gram's method, which leads to the increased possibility of 

 their being mistaken for swarms of micrococci. The peculiar 

 nature of these strange forms is as yet but very imperfectly un- 

 derstood. 



