HOW THE ANIMAL LIVES 



233 



365rt. Lymph is a product of the blood. It is a pale liquid 

 which transudes from the thin or capillary blood vessels, and is 

 used to nourish and build up the tissues. The lymphatic system 

 carries food materials to the places where they are needed. 

 S,-e 409fc. 



367. By the alimentary canal is meant the whole digestive 

 tract, beginning with the mouth, and comprising the gullet or 

 esophagus, the stomach, the small and large intestines. 



371a. The fats contain carbon, 

 hydrogen and oxygen, but the oxy- 

 gen is in small proportion. One 

 of the common fats (palmatin) has 

 the composition CoiHggOe ; another 

 (stearin) is CsiHiioOe. 



379. In physiology, the word 

 ferment is used to designate sub- 

 stances which have power to make 

 starch-like materials soluble by con- 

 verting them into sugar-like materi- 

 als. These ferments, of which ptyalin 

 is one, are secretions. They are also 

 called enzyms. These secretions 

 may be the products of cells in the 

 animal body or of independent micro- 

 organisms. The micro-organisms are themselves often called 

 ferments (35o). 



382. The single stomach of a carnivorous animal is shown 

 in Fig. 86. The stomach of a ruminant is well illustrated in 

 Fig. 87, the front walls being cut away to show the internal 

 structure. It has four divisions : C, paunch ; R, reticulum ; N, 

 manifolds ; O, the true digesting stomach. 



.'{8f>. There are various experiments which the pupil can 

 perform. Mix a little well -boiled starch with a small quantity 

 of saliva, and after a time it will be found to have become 

 sweet. If at the outset a drop of solution of iodine is added 

 to the mixture it will produce a blue color (2036). As the 

 starch is changed into sugar, this color gradually fades and i$ 

 the end disappears, 



Fig. 86. 



dog. 



