Functions of the Basal Ganglia. 6 37 



memory, or the stimulations of the past, mingle with those of the pres- 

 ent in a much larger measure, and constitute it the greatest of the inde- 

 pendent centers. Each of these centers supplements and, in some 

 measure, supercedes the one below it, at least so far as the animal func- 

 tions are concerned, for probably the vegetative functions of the medulla 

 oblongata are to be excepted. 



There is some reason to think that the corpus striatum answers to the 

 ganglion in fishes, called the ^cerebrum. If so, it is their memory or- 

 gan. In birds, too, while there is a cerebrum erected like a dome over 

 the corpus striatum, it is merely a thin shell rf and not nearly as impor- 

 tant or complete an organ as it is in the mammals, and deprivation of it 

 leaves the animal in possession of a relatively larger proportion of its 

 mental faculties. In the mammals the cerebrum has become relatively 

 greatly predominant, reaching its culmination in man. Its expansion 

 has been accompanied by a transfer to it of the highest powers of mem- 

 ory, and it has become furnished with sensory departments relating to 

 all the senses, and motor departments relating to all the animal func- 

 tions. In man and monkey, and, to a great extent, in the dog, most, 

 if not all, the original functions of the corpus striatum have been as- 

 sumed by the cerebrum, so that the services of the corpus striatum 

 could, by these animals, be largely, if not entirely, dispensed with, pro- 

 vided the organ could be eliminated without too great a shock, as actu- 

 ally happens occasionally in cases of chronic disease. 



The corpus striatum is a much more concentrated or condensed organ 

 than the cerebral hemisphere, so that the lesion of a very limited area , 

 of the former produces effects (for the time being) equal to the lesion 

 of an extensive area of the corlex. 



The Pineal Gland, or Conarium, which takes its name from its re- 

 semblance in shape to a pine cone, is, in the human subject, about the 

 size of a hazel-nut. Its use has long been a puzzle to physiologists, 

 aud it has been the subject of much conjecture. Descartes thought it . 

 to be the " seat of the soul." Its true history has only recently been 

 discovered through comparative anatomy. It is found universally 

 amongst the fishes, reptiles, birds and mammals. It lies, in man, on 

 the posterior commissure, which bridges over the fissure between the 

 posterior parts of the optic thalami. 



The Pineal gland is now shown to be the rudiment of an ancient op- 

 tic lobe. In many reptiles, such as the lizzards Hatteria and Aurelia, 

 "the pineal gland is found to be an optic lobe united to the nerve stalk of 

 a true eye, richly supplied with a branched blood vessel and nerve. Al- 

 though this eye still possesses every essential part of a visual organ, 

 yet degenerative changes have set in which show that it has been long 

 useless." In Varanus giganteus the eye has a transparent scale in place ; 



