12 FREDERICK TILNEY AND LUTHER F. WARREN 



plaque. The latter is a black spot corresponding exactly to the 

 position of the pineal gland. Duges ('29) 97 also figures the 

 same appearance in certain lizards. As early as 1835 Hollard 188 

 had made the observation that the epiphysis was entirely nerv- 

 ous in structure. He is also authority for the statement that 

 this body does not occur in fish. Gottsche ('35), 154 however, 

 states that the pineal body does exist in all fish. Valentin ('43) 403 

 concurred in Hollard' s idea, although he was of the opinion that 

 the elements in the pineal body differed considerably from the 

 gray matter of the brain. Guillot ('84) 16 makes the statement 

 that, although the pineal body exists in all vertebrates, it is not 

 until the reptiles are reached that the pineal apparatus makes 

 its appearance in most complete form. Reguleas ('45) 325 recog- 

 nized that in man the pineal body, both in its volume and form, 

 was variable. 



. Observations concerning the structural character of the pineal 

 body were made at a remarkably early period. It was not, 

 however, until the methods of histological technique were fairly 

 well advanced that much attention was devoted to the minute 

 structure of the conarium. Kolliker ('87) 212 observed two 

 types of cells in the pineal body; that is, small round cells and 

 multipolar nerve cells with compact bundles of nerve fibers. 

 These latter were few in number. From his observation Kolliker 

 was led to believe that the pineal body is entirely nervous in type. 

 Clarke ('60) 69 found nerve fibers, nuclei, and brain sand but no 

 nerve cells in the pineal body. He also observed a reticular 

 structure which resembled the olfactory mucous membrane. 

 The arrangement of the cells, he believed, was similar to that of 

 the fourth layer of the olfactory bulb in sheep and cats. 



Faivre ('55) 114 was among the first to make an extensive com- 

 parative histological study of the pineal body. He examined the 

 minute structure in man, horse, guinea-pig, dog, ox, rabbit, pig, 

 hen, turkey, dove, and tortoise. As a result of his observations, 

 he recognized three elements in the human pineal body: first, a 

 fibro vascular envelope; second, a globular parenchyma, and, 

 third, acervulus cerebri. Faivre is in general accord with 

 Valentin, in that the pineal body differs essentially from the 



