68 THE POPULAR SCIEXCE MONTHLY. 



ing whatever but mucus. As soon as articles of food made their way 

 iuto the stomach, and touched the mucous membrane, its circulation 

 grew rapid and its color lively, while peristaltic movements became evi- 

 dent. The mucous papillae then poured out their gastric juice, a clear and 

 transparent fluid, designed to dissolve the food. On wiping away the 

 mucus that covered the villous membrane, with a sponge or fine cloth, 

 the gastric juice was soon seen reappearing and gathering in little 

 drops that ran along the walls of the stomach like perspiration on the 

 face. What we have just seen as to the mucous membrane is known 

 to occur alike throughout the intestine, and in all the glandular organs 

 connected with the digestive apparatus. The salivary glands and the 

 pancreas, in the intervals of the act of digestion, present a pale and 

 bloodless tissue, the secretions of which are wholly suspended. During 

 the period of digestion, on the contrary, these same glands are swollen 

 with blood, as if inflamed and erectile, while their vessels pour out the 

 secreted fluids abundantly. 



Two orders of circulation, then, must be .recognized in the organs : 

 one, the general circulation, known since Harvey's day ; and the other, 

 local circulation, only discovered and studied in recent times. In the 

 phenomena of general circulation the blood may be said to do nothing 

 more than traverse the parts, to pass from the arteries into the veins ; in 

 the phenomena of local, which is the true functional circulation, the 

 blood penetrates all the folds of the organ, and gathers closely about its 

 anatomical elements, to arouse and excite their special mode of activity. 

 The nervous system, sensitive in its action through the vessels, gov- 

 erns all those phenomena of local circulation which attend organic ac- 

 tivity ; thus, the saliva flows copiously when a sapid substance makes 

 an impression on the nerves of the mucous membrane of the mouth, 

 and the gastric juice forms under the influence of contract between 

 food and the sensitive surface of the stomach. But, for this mechani- 

 cal excitement of the peripheral nerves of sensation, influencing the 

 organ by reflex action, a purely psychic or cerebral excitement can be 

 substituted. A simple experiment proves this : If a horse is taken 

 while fasting, and the excretory duct of the parotid gland upon the 

 side of the jaw is exposed and divided, nothing flows from it ; the 

 gland is at rest. If, now, oats are shown to the animal, or, still better, 

 if, without any thing being shown, a movement is made which leads 

 him to think he is about to have food given him, immediately a con- 

 tinuous flow of saliva issues from the duct of the parotid, and at the 

 same time the tissue of the gland is injected, and becomes the seat of 

 a more active circulation. Dr. Beaumont remarked similar phenomena 

 in his Canadian. The idea of savory food not only solicited a secretion 

 from the salivary glands, but provoked, besides, an immediate flow of 

 blood to the mucous membrane of the stomach. 



What we have just said as to the local or functional circulations, 

 applies not only to those secreting organs in which there takes place 



