144 NATURAL THEOLOGY. 



for carr^^ing on the compound motion of the lower 

 jaw, half lateral and half vertical, by which the 

 mill is worked : fountains of saliva, springing up in 

 different parts of the cavity for the moistening of 

 the food, while the mastication is going on : 

 glands, to feed the fountains; a muscular constric- 

 tion of a very peculiar kind in the back part of 

 the cavity, for the guiding of the prepared aliment 

 into its passage towards the stomach, and in many 

 cases for carrying it along that passage ; for, al- 

 though we may imagine this to be done simply 

 by the w^eight of the food itself, it in truth is not 

 so, even in the upright posture of the human 

 neck ; and most evidently is not the case with 

 quadrupeds — with a horse, for instance, in which, 

 when pasturing, the food is thrust upward by mus- 

 cular strength instead of descending of its own 

 accord. 



In the mean time, and within the same cavity, 

 is going on another business, altogether different 

 from what is here described — tliat of respiration 

 and speech. In addition, therefore, to all that 

 has been mentioned, we have a passage opened 

 from this cavity to the lungs, for the admission of 

 air exclusively of every other substance : we have 

 muscles, some in the larynx, and without number 

 in the tongue, for the purpose of modulating that 

 air in its passage, with a variety, a compass, and 

 precision, of which no other musical instrument 

 is capable. And lastly, which, in my opinion, 

 crowns the whole as a piece of machinery, we 



