Top 17 Quotes by August Krogh

The circulatory system of man and the vertebrate animals can be considered as made up of a small number of organs or subordinate systems, which are easy to recognize anatomically, and the functions of which are on the whole quite distinct.

Since muscular contractions are usually more or less regularly alternated with relaxations, the system of valves makes of the veins of every muscle a very effective pump, capable of maintaining a low pressure in the muscle capillaries.

It is no doubt technically possible to study metabolism and respiration of fishes during swimming at a constant rate, and of certain insects and birds during flight, and to obtain information similar to that obtained on man during work on a bicycle ergometer or a treadmill.

I found it possible to observe at least the superficial capillaries of muscles both in the frog and in mammals through a binocular microscope, using strong reflected light as a source of illumination. Resting muscles observed in this way are usually quite pale, and the microscope reveals only a few capillaries at fairly regular intervals.

The respiratory mechanisms of birds are definitely adapted to the function of flight, as evidenced by the fact that birds which do not fly (Apteryx, Penguins) show these adaptations in a greatly reduced form.

In the giraffe with a total height of 5 m., the heart is at a height of about 2.5 m., and it would be extremely interesting to know just how the giraffe avoids the development of filtration oedema in its long legs.