352 INTERNAL SECRETION 



but arranged irregularly, being crowded together in the interior 

 of the organ. The pineal cells have a pale tinted protoplasm and 

 very characteristic nuclei, these being large and oval, and 

 crowded, over their entire circumference, with granules. Dimi- 

 trowa distinguishes four different nucleus forms. Other im- 

 portant histological details are : (i) The peculiar nature of the 

 ependyma of the recessus pinealis, in which cubical epithelium 

 and epithelium composed of goblet-like cylindrical cells alternate ; 

 and (2) the cysts which are observed at the base and in the 

 interior of the pineal gland of new-born infants, and which 

 probably represent obliterated blood-vessels. The pineal gland 

 shows signs of involution before the age of puberty, the first 

 symptoms being observed in the seventh year. The concretions 

 known as pineal sand or acervulus, which consist of calcium 

 phosphate and calcium carbonate, are found in the glia layer 

 which covers the commissura habenularum. As age increases, a 

 distinct increase of the connective substance at the expense of the 

 glandular tissue takes place. The glandular lobes are replaced 

 by plaques composed of connective tissue and a very fibrous glia 

 tissue, and these plaques contain isolated glandular cells. The 

 connective tissue septa further undergo hyaline degeneration, and 

 may completely calcify. Occasionally, homogeneous masses are 

 observed in the septa or in the interior of the glandular lobes and, 

 after the deposition of calcium salts, corpora arenacea are evolved 

 from them. The glandular cells also present signs of involution, 

 but, even in extreme old age, glandular cells are encountered 

 which are intact and, apparently, still functionally active. Cysts 

 formed, in the majority of cases, from the glia plaques as the 

 result of obliteration of the blood-vessels, are a very common 

 finding in the pineal gland of adults. 



Physiological experiments with the pineal gland are described 

 by E. v. Cyon. This author investigated the activity of extract 

 of the pineal gland of oxen and sheep. He found that, when 

 injected intravenously, they produced no effect upon blood- 

 pressure, but that small doses accelerated the heart's action, while 

 large doses retarded and strengthened it. Irregularity of the 

 cardiac beats, bigeminal and trigeminal pulses were also fre- 

 quently observed. According to v. Cyon, extract of pineal gland, 

 when given in small doses, excites the nervi accelerantes only ; 

 in large doses it simultaneously stimulates the inhibitory cardiac 

 nerves, but in so irregular a fashion that the harmonious counter- 

 activity of the two sets of nerves is unbalanced. The cardiac 

 beats become irregular, but these irregularities disappear after 

 resection of both vagi. Further experiments showed that glycero- 

 sodium phosphate acts in the same manner as weak doses of 

 pineal extract, while glycero-calcium phosphate produces action 

 beats, as they are called, in the same way as large doses of pineal 

 extract ; but unlike those produced by pineal extract, these action 



