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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
