12 



PHYSIOLOGY. 



DIGESTION. 



A function whose end is to transform the aliment (which 

 is always animal or vegetable matter) into an opaque milky 

 fluid called chyle, capable of being absorbed by particular 

 vessels, which pour it more slowly into the circulatory cur- 

 rent; where, on mingling with the venous blood, by the 

 influence of respiration, it becomes at length arterial blood. 

 This function may be divided into seven acts : 



The taking of Aliment. 

 In man, by the hands and mouth. 



Mastication. 



The division of the food by means of small and very hard 

 bodies (the teeth), of which some (the incisors) cut, some (the 

 canine) tear, and others (the molars) grind. The teeth are 

 formed of a bony substance, covered with enamel, and having 

 within them a cavity containing a vein, artery, nerve and 

 pulpy matter. 



Insalivation. 



A liquid called saliva is imbibed by and softens the divided 

 food. The salivary glands are the parotid, the submaxillary, 

 and the sublingual, of each a pair. 



Deglutition. 



The food reduced to a soft mass crosses the isthmus of the 

 fauces, reaches the pharynx, passes upon the glottis, which is 

 covered by the epiglottis, arrives in the oesophagus and de- 

 scends into the stomach. 



Chymification. 



The action of the gastric juice, and the contractions of the 

 stomach, convert the food into a grayish pulp called chyme, 

 and propel it into the small intestines. 



Chylification. 



Under the influence of the bile and pancreatic juice the 

 chyme is now in part converted into an opaque milky liquid 

 called chyle. The organs here are the intestines, the liver 

 and the pancreas. The small intestines comprehend the du- 

 odenum, the jejunum and the ileum ; the large intestine em- 

 braces the cœcum, the colon and the rectum. 



