THE PRESIDENT'S ADDRESS. 
139 
The exact manner in which these microbes cause disease has 
not been worked out; possibly, like the putrefactive organisms, 
they take up certain elements in the media, the blood, and the 
like, in which they grow, and leave behind certain poisonous 
alkaloids. 
A very interesting enquiry is, How long can these minute 
organisms exists 
Professor Weismann, of Freiburg, in a work on the duration 
of life, says that one-celled beings, strictly speaking, do not die — 
that they are immortal. As they increase by scission or division, 
and each piece is a new life, so they may be said never to die 
except by accident. He says, "Natural death happens only to 
many-celled beings ; one-celled beings do not possess it as yet." 
The encysted stage is comparable to death. Some lower forms of 
life, as the amoebae, become motionless, and apparently enclosed, 
as it were, in a cyst; and then, as Dr. Dallinger describes it, 
suddenly a cross, as it were, is seen to appear, dividing it into 
four quarters, and then it bursts into myriads of new spores, 
which develope into fresh amoebae. Strictly speaking, then, this 
creature cannot be said to have died at all, but is really, unless 
killed by design or accidentally, immortal. 
The duration of life among many of the lower forms is much 
longer than at first sight would appear. For instance, a mollusc 
has been kept alive, I believe at Edinburgh, for more than eighty 
years. Sir John Lubbock recently had a queen ant die, which 
he had kept for fourteen years, and which was of course pre- 
sumably older. Fish again are known to be long-lived; at any 
rate, certain species. A pike was taken out of a pond in Suabia, 
which had a ring attached to it, stating that it was put in there 
by the Emperor Barbarossa two hundred years before. Again, 
amongst the higher animals elephants and parrots are very long- 
lived. The story of Humboldt's parrot is very well known. He 
found in South America a parrot which spoke, but the native 
Indians could not understand what the parrot said. It turned 
out that it was talking the language of a race of Indians which 
had been long extinct. 
According to Weismann natural death appears first amongst 
the lowest metazoa (Hetero-plastides). Somatic or body cells 
alone die, not the digestive cells. Directing all the cells to one 
generation, the somatic or real body cells endured only for a 
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