204 ANIMAL PHYSIOLOGY. [LESSON 58. 



872. The salivary glands, and their secretion, appear to be so 

 much alike, that it has been difficult to say whether they all se- 

 crete a fluid possessing the same chemical properties or not. 



873. But reasoning from analogy of the effects produced by ani- 

 mals possessing some of these glands, to the exclusion of the rest, 

 one would incline to the belief that each pair of glands possesses 

 different chemical properties, or, perhaps, that two pairs of them pos- 

 sess properties distinct from the third, and that the combination of 

 the whole is necessary to the production of the required effect. 



874. Mastication of the food, the first act in the process of di- 

 gestion, is, at the same time, the most important one. If it be per- 

 formed in a hasty, slovenly manner, dyspepsia is the unfailing result ; 

 those persons who have once accustomed themselves to consume their 

 food, dispensing with this preliminary process, never can recover the 

 lost art, and sink into an early grave, the victims of suicide. 



875. The saliva appears to possess three most important proper- 

 ties : firstly, it destroys vitality in all animal and vegetable matter ; 

 secondly, it loosens the tissues, thereby preparing them to receive 

 the saliva itself, and ultimately to admit the gastric juice; and 

 thirdly, it mechanically softens and dilutes hard or dry food. 



876. When a Cow fills her paunch with grass, she places there a 

 large amount of living vegetable material ; lying in that organ, or 

 transferring it to the second stomach, no way affects its vitality, but 

 when thrown back into the mouth, and it comes in contact with the 

 saliva, then it instantly dies, and becomes materially altered in ap- 

 pearance. 



877. Examine the contents of the first three stomachs of a Cow, 

 or a Sheep ; in the two first the food is evidently living grass, but 

 in the third it has the appearance of a thoroughly well-boiled vege- 

 table more nearly allied in color and appearance to spinach, and, 

 as yet, it has only come in contact with the saliva, which must be 

 held responsible for its changed condition. 



878. Arrest a caterpillar in the act of eating the leaf of a cab- 

 bage ; kill it instantly, open its crop, and examine the leaf you saw 

 it consume but a minute before : it will have lost its bright green 

 color, and be reduced, in every respect, to the appearance of the 

 grass in the third stomach of the Cow. As it cannot have come in 

 contact with any other material than the salivary secretion, it is 

 surely justifiable to attribute its altered appearance to the action of 

 that fluid. 



879. When man eats raw, ripe fruits,, he eats living vegetables, 



