THE PINEAL BODY 



115 



maintain that the frontal organ contains a cavity. According 

 to Leydig, this organ contains pigment in Bombinator, but 

 otherwise, in frogs, the cells are pigment-free. Histologically, 

 the cellular elements of the frontal organ show no definite 

 arrangement. These cells are usually long and their mass 

 is traversed by a few isolated fibers. deGraaf and Leydig both 

 found evidence of fatty degeneration in the organ. The so- 

 called frontal subcutaneous gland of Stieda is situated, as de- 

 scribed by that author, directly under the corium of the skin 



Po 



EpiJ 



M 



Pf V Ds Ch 



Fig. 61 The epiphyseal complex in the pineal region of Rana temporaria, ac- 

 cording to Braem, 1898. 



Ls., lamina terminalis; Pf., paraphysis; V., velum transversum; Ds., dorsal 

 sac; Po., pineal organ; N .pin., pineal nerve; Ch., commissura habenularis; Ep., 

 proximal portion; Cp., posterior commissure; M.. midbrain. 



in the midline of the head and upon a transverse line from pupil 

 to pupil. According to Lessona, 241 its position is marked by a 

 clear, white spot on the top of the head, not well developed in 

 all forms, but first described by Stieda 375 as the Scheitelfleck or 

 parietal spot. According to Leydig, 238 this spot is best made 

 out in Rana arvalis and agilis. It also occurs in Rana esculenta. 

 The stalk of the pineal organ in amphibia exists as a thin, 

 strand-like structure. Stieda 375 in 1865 first referred to it as 

 a thread connecting the frontal gland with the skull. Ciaccio 65 

 in 1867 recognized the nerve fibers in this strand. Lessona 241 in 

 1880, deGraaf 155 in 1886, and Leydig 238 in 1891, all observed the 

 nerve fasciculus in older animals, but did not appreciate its 

 significance. They thought it to be the remnant of the connect- 



