, or
take up, the chyle, and transfer it through the mesenteric glands into
the thoracic duct, through which it is conveyed into a large vein at
the lower part of the neck. In this vein the chyle is mixed with the
venous fluid. The residual matter is conveyed into the large
intestine, through which it is carried and excreted from the system.
(Appendix E.)

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What peculiar property has gastric juice? 265. Where and how is chyme
converted into chyle? What is said in regard to the bile? 266. What
becomes of the chyle? Of the residuum?

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267. In the process of digestion, the food is subjected to five
different changes. 1st. The chewing and admixture of the saliva with
the food; this process is called _mastication_.

268. 2d. The change through which the food passes in the stomach by
its muscular contraction, and the secretion from the gastric glands;
this is called _chymification_.

269. 3d. The conversion of the homogeneous chyme, by the agency of the
bile and pancreatic secretions, into a fluid of milk-like appearance;
this is _chylification_.

270. 4th. The absorption of the chyle by the lacteals, and its
transfer through them and the thoracic duct, into the subclavian vein
at the lower part of the neck.[9]

[9] The chyle is changed by the lacteals and mesenteric glands, but
the nature of this change is not, as yet, well defined or
understood.

271. 5th. The separation and excretion of the residuum.

272. Perfection of the second process of digestion requires thorough
and slow mastication. The formation of proper chyle demands
appropriate mastication and chymification; while a healthy action of
the lacteals requires that all the anterior stages of the digestive
process be as perfect as possible. (Appendix F.)

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267. Recapitulate the five changes in the digestive process.

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_Note._ Let the pupil review the anatomy and physiology of the
digestive organs from figs. 62 and 65, or from anatomical outline
plate No. 5.

[Illustration: Fig. 65. An ideal view of the organs of digestion, opened
nearly the whole length. 1, The upper jaw. 2, The lower jaw. 3, The
tongue. 4, The roof of the mouth. 5, The oesophagus. 6, The trachea. 7,
The parotid gland. 8, The sublingual gland. 9, The stomach. 10, 10, The
liver. 11, The gall-cyst. 12, The duct that conveys the bile to the
duodenum, (13, 13.