THE BEAIN IN THE EDENTATA. 301 



liinclrance in this study was the stumbling'-l)lock whicli human anatomists have erected 

 in the shape of a cerebellar anatomy which is devoid of a rational morphological basis. 

 The investigator of a large series of mammalian cerebella will aj^preciate at an early stage 

 in his labours that underlying the apparently irreconcilable differences and seemingly 

 divergent designs exhibited in cerebellar architecture there is, in all the Eutheria 

 and Metatheria, one common fundamental plan which becomes variously elaborated in 

 different animals. It thus become-; possible for him to compare upon a sure and sound 

 basis any cerebellum, ranging from the simplest bifoliate structure of Notoryctes, to the 

 most complexly elaborated organ in Man ; and it is possible to construct a simple plan 

 for descriptive purposes which will equally apply to any representative of this large series 

 of mammals. 



Since this work has been accomplished I have become acquainted with three memoirs 

 dealing with this terra iiwor/nita of cerebellar anatomy which have recently appeared. 



Thanks to the kindness of the author, I have recently received a brief introductory 

 memoir by Stroud, who has studied the development of the cerebellum in the Cat and 

 in Man *. 



This importaiit and interesting communication insists upon the uniformity of the 

 fundamental plan of the cerebellum in wZr mammals, even including the Monotremata. 

 [The writer does not refer to the distinct specialization of the Prototherian cerebellum, 

 wiiich should exclude it from this generalization.] 



A most important memoir dealing with the development of the cerebellum in the 

 Sheep and in Man appeared at about the same time as Stroud's contribution, and in many 

 points confirms, and in some other respects tends to refute, Strovid's results. Por this 

 important contribution to this much-neglected field of research we are indebted to 

 Walther Kuithan f. 



Theodor Ziehen has recently given us a pure description (unilluminated by any 

 suggestions of a general or morphological nature) of the cerebellum in the Monotremata 

 and MarsujHalia +. 



The cerebellum in Orycteropus is a large, solid, ellipsoidal mass, the major diameter of 

 which is transverse, and measures (in a specimen which had been for some years in 

 alcohol) 47 mm. ; the maximum diameter in the sagittal is 27 mm., and the maximum 

 height is 20 mm. This large, somewhat flattened mass completely covers and hides from 

 view the fourth ventricle, and it is supported on two large columns which are 11 mm. 

 apart : in other words, are 5-6 mm. from the mesial plane on each side. Each of these 

 columns is 9 mm. in diameter, and consists of the combined cerebellar peduncles of its 

 own side. It is obvious from the measurements that the cerebellum must project on 

 each side far beyond these columns of support ; but not only is this so, but its ventro- 

 lateral extremities are wrapped, as it were, around the lateral aspects of the peduncles so 



* B. B. Stroud, " The Mammalian Cerebellum. — Part I. The Development of the Cerebellum in Man and the 

 Cat," Journal of Comparative Neurology, vol. v. 1895. 



t Walther Kuithan, " Die Entwickelung des KJeiuhirns bei Saugetieren," Miinchener raedicinische Abhand- 

 lungen, vii. Reihe, 6. Heft, 1895. 



X T. Ziehen, op.cit. 



