613 
1907-8.] Middle Cells of Grey Matter of Spinal Cord. 
arising from the middle cells run in a variety of directions to begin with ; 
but as some could be traced far enough to be seen doubling more or less 
sharply upon themselves, this gives no real clue to their destination. In 
no case could I follow any one to a termination. In some cells there was 
observed an endo-cellular fibrillary network, similar to that in the large 
motor cells of the anterior horn. In this particular cord the following 
figures give approximate average diameter of the cells of the different 
groups : — 
Anterior motor cells '023-035 mm. 
Anterior central middle cells 018-023 mm. 
Central middle cells '015-018 mm. 
Post-central middle cells *01 1-015 mm. 
Apical group j intermedio-lateral "016 mm. 
Reticular group J tract '018 mm. 
Clarke’s column '020-027 mm. 
In lower sacral '010 mm. 
In conclusion, I have to express my thanks to Dr Alexander Bruce for 
suggesting this subject for a thesis ; to Dr Theodore Shennan, in whose 
laboratory the preparation of the sections was carried out ; to Mr Henry 
Wade for the use of micro-photographic apparatus; and lastly to the 
Carnegie Trust, since this thesis is part of work done under the terms of a 
grant from the Trust for original research. 
7tli July 1908. — Since this j)aper was read before the Society, Jacobsohn has 
published a paper dealing with the cells of the spinal cord (“ Uber die Kerne des mensch- 
lichen Kiickenmarks,” Anhang z. d. Abhandl. d. konigl. Preuss. Akad. der Wissenschaft, 1908). 
He describes the middle cells as the Tractus Cellularum, scattered over the whole grey 
matter, and forming no very definite groups or nuclei, but three series may be distinguished 
— (a) an antero-median group, lying along inner edge of the anterior horn ; (b) a postero- 
median group, the smallest of the three, and also composed of the smallest cells, in the 
position of, amongst, or surrounding Clarke’s column ; (c) a lateral intercornual series, the 
largest, near the formatio-reticularis, and in the outer part of the base of the posterior 
horn. All three series are indefinitely bounded towards the centre of the grey matter, 
and may meet there. 
It must be noted, however, that this author, in addition to a thoracic and a sacral 
sympathetic nucleus (intermedio-lateral tract), describes a third or lumbo-sacral median 
sympathetic nucleus, extending from L 4 to the coccygeal segment, which would include 
practically all the cells which I have described as an extension of the middle ceils into the 
lateral enlargement of the anterior horn as the motor groups die out. 
