i879-] 
or the Natural Duration of Life. 
743 
economy, destroying by fire all carriers and sources of con- 
tagion, and providing for the instant isolation of every case 
of contagious or infectious disease, they stamped out the 
communicable diseases wholesale, with a success and readi- 
ness which were surprises even to the most sanguine pre- 
ventionists, and which gained for them ten years of life. 
The science of medicine, which in its true and honest 
position is always in the front rank of advancement, was 
somewhat changed. The doctors continued to keep a cor- 
rect history of diseases, of the course of diseases, and of the 
causes of diseases, but they added an equal knowledge of 
prevention, particular and general, and valued that know- 
ledge most. Dismissing all special modes of cure by parti- 
cular systems or assumed specifics, they determined to know 
once and for ever whac diseases would not get well without 
the aid of medicines of any kind, the general conditions for 
recovery being rendered as perfect as was possible. This 
discovery of the triumph of preventive art did not, however, 
satisfy altogether. It left on record the fadt that Nature 
never goes out of her path to cure, and that what has been 
called the vis medicatrix natter ce was as much a myth as any 
other of the past myths of physic. It left on record, also, 
that under the happiest apparent external conditions some 
diseases will run their fatal course as decidedly without 
medicines as with them. 
The diseases which so progressed were, in turn, discovered 
to be diseases of what we call constitutional type, depending 
upon heredity. They were four in number : scrofula, with 
its attendant, pulmonary consumption; cancer; specific 
disease ; and insanity. The majority of the physicians, 
seeing the results I have named, began at once to teach 
that, as these diseases were obviously diseases of descent, 
and were maintained by the intermarriages of persons sub- 
ject to them, there was only one sure and certain mode of 
removing them, and that was a common-sense rule that 
such intermarriages should not be tolerated. 
The physiologists, dealing with the two questions of di- 
gestion and food for digestion, were led to the conclusion 
that a considerable shortening of life was induced by the 
excess of work which was put on the digestive organs. 
They bore in mind that many persons die from the wearing 
out of one particular organ, the rest of the organs being 
still healthy. Of all organs they agreed the stomach is 
most exposed to this danger. They found, on inquiry, that 
the stomach was distressed both by quantity and quality of 
food. Following a suggestion thrown out by Flourens, they 
