CHAPTER LXXXV 



THE PINEAL GLAND 



This peculiar structure lies between the anterior corpora quadrigem- 

 ina, and weighs about two-tenths of a gram. It is largest in the early 

 years of life, and undergoes retrogressive changes after puberty. Micro- 

 scopically it consists of epithelial cells arranged loosely in trabeculse, 

 with large sinus-like capillaries between them; neuroglia and sometimes 

 muscle-fiber cells are also present. Curious globules of calcareous mat- 

 ter (brain-sand) are also found, especially in the pineal gland of man. 

 The gland is developed from an evagination of the third ventricle, and 

 vt is homologous with the so-called median eye of reptiles. 



The functions of the pineal gland are obscure. In cases where its 

 extirpation has been successfully accomplished (in the fowl), it has been 

 found that the body growth is stimulated and the sexual characteristics 

 developed more quickly. This result would seem to indicate that the 

 clinical observation that tumors of the pineal gland are associated in 

 young boys Avith abnormal growth of the skeleton and with the early 

 development of the secondary sexual characteristics, depends on the 

 fact that a condition of hypopinealism is produced by the growth of a 

 tumor. The immediate effects of the injection of extract of pineal gland 

 are not characteristic, consisting merely of a fall in blood pressure, which 

 is,- however, obtainable when an extract of practically any cellular organ 

 is injected. Prolonged administration of an extract to growing animals 

 is said to accelerate the growth and to bring about a precocious develop- 

 ment of the sexual organs; but this result is somewhat difficult to inter- 

 pret, for, as we have just seen, similar changes occur after experimental 

 removal of the gland. 



THE GONADS OR THE GENERATIVE ORGANS 



The Generative Glands of the Male 



The structures which are responsible for the well-known influence of 

 the testicles on the development of the male sexual characteristics are 

 the so-called interstitial cells of Leydig, which consist of polygonal- 

 shaped epithelial-like cells, with well-marked nuclei and nucleoli. Lipoid 



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