Till canker taints the vegetable blood,

Mines round the bark and feeds upon the wood;

So years successive from perennial roots,

The wire or bulb with lessened vigour shoots,

Till curled leaves or barren flowers betray

A waning lineage verging to decay;

Or till amended by connubial powers,

Rise seedling progenies from sexual flowers."

The minute nature of the germs of disease preclude all possibility of their being submitted, as far as we know at present, to the inspection of the physiologist, but we may infer many facts from results. In the same way, though with humbler

ideas, as Cuvier could build up an animal from a single bone, can we by a combination of facts infer the existence of living beings and conjecture their forms. "The re-production or generation of living organized bodies is the great criterion or characteristic which distinguishes animation from mechanism." We find the virus of Small Pox, according to Mr. Ceely's experiments, developing itself as a constitutional disease upon the cow, and becoming modified into a form known as the Cow Pox; this resembles the process of cultivation by which a species is converted into a variety, this variety remains for a certain time persistent; the time is not yet known, but it is known that by degrees, as stated above, a deterioration occurs, and fertility becomes impaired, "a waning lineage verging to decay," and this has been observed as a feature in the result of vaccination. I believe Dr. Gregory was one of the first to notice this fact, and deemed it necessary to obtain fresh lymph from the cow; this has been done, and it is not improbable, if the analogy we have drawn be correct, that the slowly spreading scepticism regarding vaccination may be arrested in its progress. If we can explain the deterioration of cow pox virus on this principle we have a hold at once upon the public, and can assure them that the efficacy of the proceeding is as certain as in the time of Jenner. The people, I contend, have a right to demand of us the reason why vaccination is not so efficacious as formerly, and I