[ 911 ] 
XXXVI. Researches on the Development of the Spinal Cord in Man, Mammalia, and 
Birds. By J. Lockhakt Claeke, F.B.S. 
Eeceived May 29, — ^Eead June 19, 1862. 
In’ the Philosophical Transactions for 1859, I showed that, in the adult spinal cord of 
Man and all vertebrate animals, the white columns as well as the grey substance are 
everywhere interspersed with granular nuclei, of which some are attached to the sheaths 
of the primitive nerve-fibres, while others are imbedded in the intervening connective 
tissue. In the grey substance these nuclei are more abundant than in the white, and 
have much resemblance to many of the free nuclei or cells, which are certainly in con- 
nexion with nerve-fibres, and with which they are freely intermixed. With the hope 
of throwing some light on the histological relation between these and the other elemen- 
tary tissues of the cord, the following inquu’ies into their development were under- 
taken. 
The histology of the development of the spinal cord in Birds and the higher animals 
had already been begun by Bidder and Kupffer*, and pursued a little further by 
Kolliker. The results of their investigations are comprised in the following statements : 
1. After the closing of the laminoe dorsales, the cord at first consists of a canal, the 
walls of which are composed of cells of one uniform kind, and disposed in a radiating 
form. 
2. In the next place, this wall of cells divides into two layers, of which the outer 
forms the grey substance, while the inner one appears as the lining of the central canal. 
3. The white substance makes its appearance later than the grey, by the cells of 
which it is without doubt furnished as an outer layer or covering. __ The white columns 
are four in number, two on each side; and to these a white commissure is added. 
There are no lateral columns ; those which are so called are subsequently formed as an 
extension of the anterior columns f. 
The investigations of which I now communicate the results were made on embryos of 
the domestic fowl, of the Sheep, Pig, Ox, and Man. The fiuid emjDloyed in the process 
of hardening was at first a weak solution of bichromate of potash, and then a similar 
solution of chromic acid. Wlien sufficiently young, the embryos were immersed in 
the solution without mutilation ; but in the more advanced states of development the 
spinal cord was previously uncovered. 
* UntersucliuDgen iiber die Textur des Kiickenmarks, und die Entwickelung seiner Eormelemente. 
Leipzig, 1857. 
t Kollikee, Entwickelungsgeschickte des Menschen und der hoheren Thiere. Leipzig, 1861, pp. 259, 260. 
MDCCCLXII. 6 I 
