Re: 'Fast Facts' on the circulatory systems of the tiger, snake, and jaguars.

You guys have stumped me on this one. You picked some difficult animals to ask these questions about. The large cats, like jaguars and tigers are not listed in my anatomy and physiology books. As far as snakes go, it is important to realize that they come in all sizes. Their anatomy and physiology will depend on which type of snake you are talking about.

In general, the snake heart is a little different than that of a mammal. Snakes have a four chambered heart (2 atria and 2 ventricles), but the dividing wall (septum) between the 2 ventricles is incomplete. Some blood returning from the body's tissues enters the ventricles and is pumped back to the body, directly. This allows blood to bypass the lungs during hybernation, exercise and during diving as happens in other reptiles such as turtles. Reptile lungs are like simple sacs. The right lung is larger in all snakes. Reptiles also do not have a diaphragm (the muscle we use during *inspriation* to breathe).

I am sorry that I cannot find the information you requested. But I thought that you might be interested in looking at the heart of a pig. Also, the average weight of the hearts of some other species are as follows:

Horse - 4 kg or 0.7% of body weight
Dog  - 1% of the dog's body weight
Cow - 2.5 kg or 0.5% of body weight
Pig - 0.5 kg or 0.25% of body weight