ed a lacteal. The lacteals run together into larger
and larger branches until they form a main trunk, the thoracic duct,
which opens into the blood circulation at a point near the heart; but
of this we shall speak further later. They contain, after a meal, a fluid
called chyle.

Section 31. Emulsified fats pass into the chyle. Water and diffusible
salts certainly pass into the vein. The course taken by the peptones
is uncertain, but Professor Foster favours the chyle in the case of
the rabbit-- the student should read his Text-book of Physiology,
Part 2, Chapter 1, Section 11, if interested in the further discussion
of this question.

Section 32. The processes that occur in the remaining portions of
the alimentary canal are imperfectly understood. The caecum is so
large in the rabbit that it must almost certainly be of considerable
importance. In carnivorous animals it may be so much reduced as to
be practically absent. An important factor in the diet of the
herbivorous animals, and one absent from the food of the carnivora,
is that carbohydrate, the building material of all green-meat- [food],
cellulose, and there is some ground for thinking that the caecum is
probably a region of special fermentive action upon it. The pancreatic
juice, it may be noted, exercises a slight digestive activity upon this
substance.

Section 33. Water is most largely absorbed in the large intestine,
and in it the rejected (mainly insoluble) portion of the food gradually
acquires its dark colour and other faecal characteristics.

3. _The Circulation_

Section 34. The next thing to consider is the distribution of the food
material absorbed through the walls of the alimentary canal to the
living and active parts of the body. This is one of the functions of the
series of structures-- heart and blood-vessels, called the circulation,
circulatory system, or vascular system. It is not the only function.
The blood also carries the oxygen from the lungs to the various parts
where work is done and kataboly occurs, and it carries away the
katastases to the points where they are excreted-- the carbon
dioxide and some water to the lungs, water and urea to the kidneys,
sulphur compounds of some kind to the liver.

Section 35. The blood (Figure 4, Sheet 2) is not homogeneous;
under the low power of the microscope it may be seen to consist of--

(1.) a clear fluid, the plasma, in which float--

(2.) a few transparent colourless b