- 04 TEXT-BOOK OF PHYSIOLOGY 



the cardio-inhibitor center as the retardation is partly prevented at least 

 when the vagus is divided or its function suspended by atropin. Even after 

 this has been done, however, a slowing of the heart may still be induced, a 

 fact which suggests that the extract acts directly on the heart-muscle as well. 

 Schafer and his co-workers have also demonstrated that pituitary extracts 

 causq dilatation of the renal vessels and stimulate specifically the renal cells 

 to activity, thus causing a marked diuresis. The extract also stimulates the 

 non-striated muscles of the intestines, bladder and uterus, giving rise in each in- 

 stance to vigorous contractions; it also causes a marked discharge of milk 

 from the mammary gland during lactation due to the contraction of the walls 

 of the milk ducts; the dilatator muscle of the iris is also stimulated, causing 

 dilatation of the pupil. A pharmaceutical preparation of the pituitary, 

 "pituitrin", in a similar manner raises the blood-pressure for a considerable 

 period, stimulates intestinal peristalsis and excites contractions of the uterus 

 during and after labor. 



The Functions of the Pituitary or Hypophysis. The functions of the 

 pituitary body are related to the activities of the anterior and posterior lobes. 

 The anterior lobe, through its internal secretion stimulates the growth of the 

 skeleton and associated tissues as apparently shown by the fact that an excess 

 of secretion in early life leads to giantism and in adult life to acromegaly, 

 while a detkiency of secretion leads to defective growth and the establish- 

 ment of infantilism. The posterior lobe through its internal secretion assists 

 in the regulation of carbohydrate metabolism as shown by the fact that an 

 excess of secretion lowers the assimilation capacity and thus develops gly- 

 cosuria, while a deficiency of the secretion raises the assimilation capacity 

 and leads to the production and accumulation of fat. 



ADRENAL GLANDS 



The adrenal glands or suprarenal capsules are two flattened bodies, some- 

 what crescentic or triangular in shape, situated each upon the upper extremity 

 of the corresponding kidney, and held in place by connective tissue. They 

 measure about 40 mm. in height, 30 mm. in breadth, and 6 to 8 mm. in 

 thickness. The weight of each is about 4 gm. Accessory glands are some- 

 times found in the surrounding connective tissue along the abdominal sym- 

 pathetic and in the neighborhood of the genital organs. 



In some animals such as the dog, cat and rabbit, these glands have no 

 anatomic connection with the kidneys, but are situated at varying dis- 

 tances from them. 



Histology. The gland is covered externally by a capsule of fibrous 

 tissue from which septa pass into the more central portions thus forming a 

 framework for the support of blood-vessels and cells. 



A section of the gland shows just beneath the capsule an outer portion 

 termed the cortex and an inner portion termed the medulla (Fig. 222). The 

 cortex consists mainly of cuboid cells arranged in cylindric columns. The 

 outer layers of cells are arranged in irregular masses forming what has been 

 called the zona glomerulosa. The medulla consists of uniting and interlacing 

 cords of polyhedral cells, the cytoplasm of which contains granular matter 

 and a distinct nucleus. When treated with chromic acid or chromium salts 

 the cytoplasm stains a dull brown or yellow color. For this reason they are 

 termed chromaffin cells. Similar cells are found in sympathetic ganglia. 



