152 PRINCIPLES OF PHYSIOLOGY 



pressure of the blood in the great vessels is 

 much increased, a condition, within limits, 

 favourable to a vigorous circulation. Adrena- 

 lin is now used medicinally, as a powerful 

 styptic by which bleedings may be arrested. 

 This is a striking example of a so-called internal 

 secretion. 



82. Similarly the pituitary body appears to 

 exert an influence on the growth and develop- 

 ment of bone, and morbid conditions of the 

 organ are apparently related to a curious 

 disease called acromegaly, in which the bones 

 of the face and fingers in particular become 

 enormously developed. This subject, how- 

 ever, is still obscure. 



83. Another organ which is the seat of 

 many hidden processes is the spleen. It is 

 the largest of the ductless glands. It has 

 a strong fibrous capsule, and passing from 

 the capsule in all directions into the interior 

 of the organ we find septa or partitions of 

 connective tissue and unstriated muscle, 

 dividing the organ into numerous compart- 

 ments. These are filled with spleen pulp. 

 This pulp consists of finer fibres forming a 



