Physiology

Did you ever look through a good microscope at the thin transparent web of a frog’s foot, and watch the red blood coursing along its narrow channels? If not, go and look at it a...

If you look carefully you will see that the cavity is divided into two by a cross partition (Fig. 1, _B_) called the =diaphragm=. The part =below= the diaphragm is the larger of...

the intestine. These are called =villi=; they are not unlike the papillæ of the skin (Fig. 15), if you suppose all the epidermis stripped except the bottom row of cells (_d_), a...

Take the bones of the arm; fix the top end of the humerus; tie it to something so that it cannot move. Fasten a piece of string to either the radius or ulna (it doesn’t matter w...

On the right side of the heart we have, then, two great valves, the tricuspid valve between the auricle and the ventricle, and the semilunar valve between the ventricle and the...

Now to return to our muscle. When you were watching the circulation in the frog’s foot, you could tell the artery from the vein, because in the artery the blood was flowing _to_...

Thus it comes to pass that the tidal air, which at each pull of the diaphragm and push of the sternum goes into the chest as pure air with twenty-one parts oxygen to seventy-nin...

The volume is as practical as possible. To aid the student in identifying the stars and constellations, the fine Celestial Charts of Arago, which answer all the purposes of a co...

=27.= Go and ask the butcher for a sheep’s pluck. There will most probably be one hanging up in his shop. Look at it before he takes it down. The hook on which it is hanging has...

In this volume much more space has been devoted, comparatively speaking, to the Invertebrate Animals, than has usually been the case in works of this nature: upon the belief tha...