96 USE OF THE CAPILLARY VESSELS. 



entirely distinct system. So extensive is their distribu- 

 tion, that the most important organs of the body seem to 

 be almost wholly made up of an immense network of 

 capillary vessels. Owing to their exceeding minuteness, 

 some of them carry only the colorless portions of the 

 blood, the red globules being too large for their calibre. 

 In inflammation, where the vessels are enlarged, those 

 which before transmitted only the colorless portions, 

 may now be seen carrying the red globules as you 

 may have observed in inflammations of the eye. The 

 motion of the blood in these vessels is beyond the influ- 

 ence of the heart, and under the entire control of the 

 vessels themselves. This independence of action may 

 be witnessed in those distributed to the face, which a 

 sudden emotion of mind will distend to redness with the 

 rapidity of thought. 



Emily. And pray, Dr. B., what may be the office 

 of this extensive system of vessels ? One would think 

 they were designed for some very important and won- 

 derful end. 



Dr. B. And he would think perfectly right, for they 

 are the seat of some of the most important functions in 

 the animal economy. From them the peculiar fluids 

 are secreted, the body is nourished, and many other 

 processes are probably accomplished which the research- 

 es of physiology have not yet unfolded to view. Their 

 number is considerably greater, where secretion is to be 

 performed, than where their object is only the nutrition 

 of the part. It is for this reason that the liver, stomach, 

 &LC. which secrete certain fluids that are essentially nec- 

 essary to the system, are supplied with a greater quan- 

 tity than the bones, ligaments and skin. 



Their action in repairing injuries of parts, is one of 

 great use in the animal economy, and presents some 

 very interesting; and curious facts. When any part is 

 injured, the capillaries are enlarged and distended with 

 blood ; serous and fibrous portions of the blood are pour- 

 ed out ; and heat, pain, redness, and swelling are soon 



