Don't become a mere recorder of facts, but try to penetrate the mystery of their origin.
Ivan Pavlov
Perfect as the wing of a bird may be, it will never enable the bird to fly if unsupported by the air. Facts are the air of science. Without them a man of science can never rise.
While you are experimenting, do not remain content with the surface of things.
Appetite, craving for food, is a constant and powerful stimulator of the gastric glands.
It is not accidental that all phenomena of human life are dominated by the search for daily bread - the oldest link connecting all living things, man included, with the surrounding nature.
But man has still another powerful resource: natural science with its strictly objective methods.
Physiology has, at last, gained control over the nerves which stimulate the gastric glands and the pancreas.
It is clear to all that the animal organism is a highly complex system consisting of an almost infinite series of parts connected both with one another and, as a total complex, with the surrounding world, with which it is in a state of equilibrium.
From the described experiment it is clear that the mere act of eating, the food even not reaching the stomach, determines the stimulation of the gastric glands.
Our success was mainly due to the fact that we stimulated the nerves of animals that easily stood on their own feet and were not subjected to any painful stimulus either during or immediately before stimulation of their nerves.
Only by observing this condition would the results of our work be regarded as fully conclusive and as having elucidated the normal course of the phenomena.
The physiologist who succeeds in penetrating deeper and deeper into the digestive canal becomes convinced that it consists of a number of chemical laboratories equipped with various mechanical devices.
Finally, as the digestive canal is a complex system, a series of separate chemical laboratories, I cut the connections between them in order to investigate the course of phenomena in each particular laboratory; thus I resolved the digestive canal into several separate parts.
It goes without saying that the desire to accomplish the task with more confidence, to avoid wasting time and labour, and to spare our experimental animals as much as possible, made us strictly observe all the precautions taken by surgeons in respect to their patients.
It has long been known for sure that the sight of tasty food makes a hungry man's mouth water; also lack of appetite has always been regarded as an undesirable phenomenon, from which one might conclude that appetite is essentially linked with the process of digestion.
As was to be expected, the discovery of the nervous apparatus of the salivary glands immediately impelled physiologists to seek a similar apparatus in other glands lying deeper in the digestive canal.
Our experiments not only proved the existence of a nervous apparatus in the above-mentioned glands, but also disclosed some facts clearly showing the participation of these nerves in normal activity.
Edible substances evoke the secretion of thick, concentrated saliva. Why? The answer, obviously, is that this enables the mass of food to pass smoothly through the tube leading from the mouth into the stomach.
The digestive canal represents a tube passing through the entire organism and communicating with the external world, i.e. as it were the external surface of the body, but turned inwards and thus hidden in the organism.
In the case of the stomach, however, the nerves of the glandular cells were always severed when constructing an artificially isolated pouch and this, naturally, affected the normal work of the stomach.
The gastric laboratory uses its protein ferment under an acid reaction.
Thanks to our present surgical methods in physiology we can demonstrate at any time almost all phenomena of digestion without the loss of even a single drop of blood, without a single scream from the animal undergoing the experiment.
