It has long been known that the sea lamprey, Petromyzon marinus, during the spawning season, when the body is distended with eggs, takes no food, and that the digestive tract during this period shrivels up until it is reduced to a mere thread. This condition doubtless obtains in other forms as well, though it has not been actually observed by the writer elsewhere.
A number of small alligators that were kept alive in the laboratory for a year or more caused the writer to wonder whether any very marked change had taken place in their digestive tracts during the months they took no food.
In captivity, especially if the water in their tank be kept cold, alligators may refuse food for five or sixth months. Whether, during the winter months, in their native haunts, they entirely cease feeding, the writer has had no opportunity to observe, though it is popularly reported that such is the case.
The first alligator from which tissues were taken was about a year and a half old, and measured eighteen inches in length. It was killed in March after a fast of several months, probably four or five, possibly more, though it was not in the writer’s possession for so long a time.
Fig. 35. Outline of Digestive Tract
Fig. 35. A diagrammatic outline of the digestive tract of the alligator from the beginning of the œsophagus to the cloaca, to show the planes of the sections that were studied, a.oes., anterior œsophagus; a.r., anterior rectum; a.s.i., anterior small intestine; c.st., cardiac stomach; f.st., fundic stomach; m.s.i., middle small intestine; p.oes., posterior œsophagus; p.r., posterior rectum or cloaca; p.s.i., posterior small intestine; p.st., pyloric stomach.
Although carefully fixed in the usual fluids, the epithelial structures from this animal were not as clearly defined in most cases as could be desired; this rather unsatisfactory fixation may have been due to some physiological condition characteristic of the period of hibernation. That this was the case seems likely from the better fixation obtained by the same methods in the case of animals killed during the feeding season.
The other animals from which tissues were taken were considerably smaller than the one mentioned above. They were killed early in the fall, after having been fed regularly for about five months upon bits of meat, both raw and cooked.