tion (i. e., interchange of gases in the lungs) there is, when the thoracic muscles and diaphragm are not acting (i. e., complete cessation of movement) is maintained principally by the "cardio-pneumatic" movement.[1] A hibernating dormouse may not give a single respiration for ten minutes, then takes from ten to fifteen breaths, at the end of which it again lapses into a state of quiescence for a period of several minutes, when the spasmodic respiratory act again occurs. The same animal, when in a normal waking state, breathes at the rate of eighty or more respirations a minute. Similar results are obtained in other animals. It has been observed that hibernating bats and marmots could be kept for hours in an atmosphere of carbon dioxide gas, without suffering any ill effects, whereas a bird or rat placed in the same chamber died almost at once, thus showing that in the hibernating state the consumption of oxygen is extremely small or in other words very little oxygen is required by the hibernating animal (owing to the quiescence and lowered metabolism of the animal and naturally for the same reasons very little carbon dioxide is given off). Saissy has observed that the amount of oxygen taken in by a dormouse varied according to the activity of the animal, and so in true hibernation the amount of the intake of oxygen is naturally very small.
Circulation
During hibernation, the force and frequency of the heart-beat is greatly reduced. In the case of the bat and dormouse, it is as low as fourteen or sixteen per minute, while in these animals in the active state it is one hundred and over. Hill and Pembry by applying a stethescope to the chest of a hibernating bat, make the observation that no sound of the heart-beat could be heard, I can confirm this observation as applying to the hibernating ground-hog in British Columbia, also, whereas with the animal awake and active, the sounds were so loud that they could be heard distinctly when the ear was an inch away from the animal.
I have found, and can confirm other observers, that the blood during hibernation has an arterial hue (bright red) in the veins, and, on the other hand, Marshall Hall states that it has a venous color in the arteries.
Digestion
The activities of the digestive organs vary according to the habits of the different animals. Some, much as the dormouse, marmot (?) and hamster, store up food in the autumn which they consume during the winter in their waking intervals. Naturally, then, their digestive
- ↑ Cardio-pneumatic movement. Here the visible movements of respiration, dilation and contraction of the thorax, have ceased, but still air (a very small amount) is drawn into and expelled from the lungs. This is due to the heart's action, it also being contained in the thoracic cavity, hence its contraction and dilation so alters the pressure in the thorax that an interchange of respiratory gases is produced in the lungs.
