THE PINEAL BODY 11 



the fetus, but after the seventh year of life this element makes 

 its appearance and tends to increase until old age. Cruveilhier, 72 

 in his description of the conarium, drew attention to a cavity 

 situated near the base of the structure which frequently con- 

 tained a fluid. Gratiolet, 157 referring to this cavity, described 

 it as the ventricle of the pineal gland. 



Majendie, (1795) 257 commenting at considerable length upon 

 the hypothesis of Descartes concerning the seat of the soul, 

 ingenuously remarks that he himself has a better conception of 

 the nature and function of the pineal body which he desires to 

 substitute for the theory of Descartes. His own suggestion, 

 says Majendie, is not only very simple, but actual and true, for 

 it must be obvious from the situation as well as from the struc- 

 ture and form of the pineal body that it serves as a tampon 

 designed to expand and in this way to close off the aqueduct of 

 Sylvius or, at other times, shrinking, to permit this aqueduct to 

 open again so that the fluid in the ventricles may have free 

 access from the third chamber to the fourth. Majendie, how- 

 ever, does not state upon what grounds the internal structure of 

 the pineal body justifies such a belief, but he is none the less 

 emphatic in calling attention to the valve-like nature of the 

 conarium with reference to the cerebrospinal fluid. 



Gunz (1753) m attributed dementia to impeding of the flow of 

 spirits caused by the pineal body. Burdach ('19-'26) 48 con- 

 sidered the pineal body as supplementary to both the cerebellum 

 and cerebral hemispheres. Tiedemann ('23) 395 found the epi- 

 physis in reptiles, birds, and mammals. Serres ('24-'28) 353 and 

 Willis 429 both make the statement that the epiphysis occurs in 

 fish, birds, and reptiles in fact, in all classes of vertebrates. 

 Andral ('29) 4 also described the organ as occurring in all the 

 classes of vertebrates. Brandt ('29) 40 recognized a glandular 

 structure under a small scale in the head of Lacerta agilis which 

 corresponded to a circular depression in the parietal region of 

 the skull. This he regarded as a special gland. Milne-Edwards 

 ('29), 107 in his researches on lizards, figures but does not describe 

 certain plaques in the head of these animals. He indicates these 

 as the occipital plaque, the parietal plaque, and the interparietal 



