Abstract
As regards the saccharifying power of the saliva of the horse, various opinions have hitherto been published, but it is now widely known that the power is not a strong one. This has also been proved by the author's investigation. It is generally believed, on the other hand, that the starch digestion which takes place in the stomach of the horse is chiefly due to the action of ptyalin. This contradiction was the motive by which the author began to set his hand to the study of saccharization of food in the stomach. Having made a series of experiments the author has found that the starch digestion in the stomach is by no means due to the action of ptyalin but to an enzyme contained in the bronchial mucus. This enzyme, according to the author's experiment, has a strong saccharifying power and gives rise to the saccharization of food in the stomach. The author called the enzyme "lung amylase" after its origin. The following is the brief description of the experiments.
1) 50c.c. of 1% starch solution, added with 0.25g. of mucus taken from the surface of the tracheal mucous membrane, has been completely saccharized at 37°C in one hour on an average (20 minutes to 3 hours in 13 cases)
2) A piece of lung tissue taken from a horse killed by bloodletting was cut into smaller pieces and extracted with twice as much water as the volume of the piece. 50c.c. of 1% starch solution, added with 5c.c. of the extract, has also been converted into sugar at 37°C in 42 minutes on an average (15 minutes to 2 hours in 9 cases), while it has taken 10 hours and 20 minutes to saccharify the same starch solution by an addition of 5c.c. of horse serum, that means, the saccharifying power of the serum is about 1/150 as weak as that of the extract of lung tissue. From this fact it will be seen that the saccharifying power of the extract is not due to the action of serum amylase.
3) A tracheotomy was performed in the upper and lower part of the trachea and the communication between these two parts was shut putting a tamponade in the middle part. It was noticed, as the result of this operation, that the saccharifying power of the mucous substance taken from the upper part of the trachea became very weak and after 4-24 hours almost disappeared. It has been shown further that even after several hours no increase in the saccharifying power was constated in the mucus taken from the upper part which was then communicated with the lower part by means of a gummi tube to allow the air to pass through it. As for the saccharifying power of the mucus from the lower part no change has been resulted by the operation.
It may be thought from the foregoing that the amylase which is found in the tracheal mucus must be secreted in the lung, because there cannot be found any difference between the histological structure of the upper part and that of the lower part of the trachea.
4) The saliva taken from the oesophagus of a horse, intratracheally injected with a certain quantity of carmin solution, then stimulated to an increased secretion of saliva was coloured with carmin and proved to have a strong saccharifying power. A starch ball which was then given to the horse and taken from the oesophagus was also coloured with carmin. It has been found, moreover, that in the starch chyme which was kept at 37°C for one hour a large quantity of sugar was present. When oat was given, instead of starch ball, it was noticed that an increased quantity of carmin came out of the oesophagus.
The experiments, in which no injection of carmin was performed, gave the similar result, that is, no particular change was observed as regards the saccharifying power of saliva and the sugar formation in the chyme.
5) In the case of a horse in which the trachea was stopped in its upper part so as to prevent the forthcoming of the mucus from the trachea into the pharynx,
