Scottish National Antarctic Expedition : A Contribution to the Histology of 

 the Central Nervous System of the Weddell Seal (Leptonychotes weddellii). 

 By Harold Axel Haig, M.B., B.S. (Lond.), M.R.C.S. (Eng.), L.R.C.P. (Lend.), 

 Lecturer in Histology and Embryology, University College, Cardiff. Communi- 

 cated by Dr W. S. BRUCE. (With Two Plates and Nine Text Figs.) 



(MS. received June 18, 1912. Read December 2, 1912. Issued separately February 17, 1913.) 



CONTENTS. 

 PART I. (/) The Cerebellum. 



(<i) The Spinal Cord. 



(6) The Medulla Oblongata. 



(c) The Pons Varolii. 



The Mesencephalon. 



() The Motor Cortical Area. 



(g) The Optic Thalamus. 



The Pituitary Gland. 



PART I. 



INTRODUCTORY AND PRACTICAL DETAILS. 

 The specimens submitted for examination were : 



(a) Portions of the brain (labelled Specimen XXXI.). 

 (6) Portions of spinal cord (labelled Specimen XXIV.). 



Both were in excellent condition as regards fixation and hardening, having been 

 preserved for many years in a fluid composed of formol and 95 per cent, alcohol (the 

 fluid was also injected into the cerebral vessels). They were, previous to histological 

 examination, submitted to the following processes : 



i. Comparatively thin slices were taken from various regions and placed for 



twenty-four hours in absolute alcohol, 

 ii. Then transferred to acetone for twelve hours, 

 iii. Placed in xylol until permeated. 



iv. Embedded in paraffin of melting-point 52 C. Sections were then taken 

 with an improved form of the Cambridge rocking microtome, and fixed to 

 slides by means of the albumen method. 



Staining of the Sections. 



The best stain for differentiating the grey and white matter was found to be 

 Weigert's method with acid fuclisin, used alone, or subsequent to treatment with 

 Delafield's haematoxylin. Other stains were tried (Bismarck brown with acid fuchsin 

 as counterstain, aniline blue-black, haematoxylin and orange-G., etc.), but acid-fuchsin 



(REPRINTED FROM THE TRANSACTIONS Of THE ROYAL SOCIETY OF EDINBURGH, VOL. XLVm., PP. 849-866.) 



