144 



VACCINE LYMPH. 



cannot be distinguished from ordinary pus. It differs 

 indeed from this last, but not in appearance, chemical 

 composition, or physical properties. It differs in 

 vital power. 



Vaccine Lymph. Vaccine lymph which has been 

 just removed from the growing vesicle will be found 

 to contain a great number of extremely minute par- 

 ticles of bioplasm, which may be well seen under a 

 power magnifying from i,ooo to 2,000 diameters. In 

 1863 I made a drawing of the appearances I observed 

 in the bioplasts from a drop of perfectly fresh lymph 

 which had been transferred to a warm glass slide, and 

 carefully covered with very thin glass, under the ^ 

 object glass, which magnifies about 1,800 diameters. 

 The results are represented in Fig. 61, plate XVII, 

 which was published in the " Quarterly Journal of 

 Microscopical Science" for April, 1864. 



In vaccine lymph which has been kept for some 

 time in glass tubes, multitudes of very minute par- 

 ticles are observed, and these exhibit the most active 

 molecular movements. These particles have often 

 been termed debris, and have been regarded as quite 

 unimportant elements of the lymph. To them, how- 

 ever, the active properties of the lymph are entirely 

 and solely due. And I should be no more inclined, 

 in the absence of the most positive evidence to the 

 contrary, to regard the fluid portion of the vaccine 

 lymph as the active material, than I should be to 

 assume that the fluid in which the spermatozoa were 



