THE BRAIN OF A FQTAL OkNITHORHYNCHUS. 181 
The Brain of a Fetal Ornithorhynchus.' 
Part I.—The Fore-brain. 
By 
G&. Elliot Smith, Wi.D., Cia. i., 
Demonstrator of Anatomy, University of Sydney, N.S.W. 
With Plate 11. 
Tue foetus, with whose brain this paper is concerned, was 
received already preserved in alcohol from the Australian 
Museum of Sydney by Professor J. 'T. Wilson, who has 
described in full the external appearances and measurements.” 
It is sufficient here to mention that its extreme length, mea- 
sured along the dorsal contour, is 80 mm. | 
The head was split sagittally some distance from the middle 
line, and the larger piece, after being embedded in celloidin, 
was cut in a complete series of coronal sections, each 50 1 
thick. These were stained with haematoxylin and decolourised 
with alcohol acidulated with picric acid, which afforded a very 
useful counter-stain. By means of the picric stain the nerve- 
fibres were clearly demonstrated, so that it was easy to make 
out their general distribution sufficiently accurately to compare 
1 This paper forms part of a thesis dealing with the ‘ Anatomy and Histology 
of the Cerebrum of the Non-placental Mammal,” which was awarded the 
University Medal when presented to the examiners for the M.D. degree at 
the University of Sydney, March, 1895. ‘The account of the gross anatomy 
is now being published elsewhere. ‘The account of the histology of the adult 
brain will be published shortly. 
2 « Description (with figures) of a Young Specimen of Ornithorhynchus 
anatinus,” ‘Proceedings of Linnean Society N.S.W.,’ vol. ix, part 4, 2nd 
series) p. 682. 
