242 ( 2 g ) 



tent to produce a whole crop of acorns, each gifted with 

 the power of reproducing its parent tree, and as thus 

 from a single seedling a whole forest may spring, so 

 these epidemic diseases literally plant their seeds, grow, 

 and shake abroad new germs, which, meeting in the 

 human body their proper food and temperature, finally 

 take possession of whole populations. Thus Asiatic 

 cholera, beginning in a small way in the Delta of the 

 Ganges, contrived in seventeen years to spread itself 

 over nearly the whole habitable world. The develop- 

 ment from an infinitesimal speck of the virus of small- 

 pox of a crop of pustules, each charged with the orig- 

 inal poison, is another illustration. The reappearance 

 of the scourge, as in the case of the Dreadnought at 

 Greenwich, reported on so ably by Dr. Budd and Mr. 

 Busk, receives a satisfactory explanation from the theory 

 which ascribes it to the lingering of germs about the in- 

 fected place. 



Surgeons have long known the danger of permitting 

 air to enter an open abscess. To prevent its entrance 

 they employ a tube called a cannula, to which is at- 

 tached a sharp steel point called a trocar. They punc- 

 ture with the steel point, and by gentle pressure they 

 force the pus through the cannula. It is necessary to 

 be very careful in cleansing the instrument ; and it is 

 difficult to see how it can be cleansed by ordinary 

 methods in air loaded with organic impurities, as we 

 have proved our air to be. The instrument ought, in 

 fact, to be made as hot as its temper will bear. But 

 this is not done, and hence, notwithstanding all the sur- 

 geon's care, inflammation often sets in after the first op- 

 eration, rendering necessary a second and a third. 

 Rapid putrefaction is found to accompany this new in- 



