View source for Paper - Cell columns in the spinal cord of a human foetus of fourteen weeks

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=Cell Columns in the Spinal Cord of a Human Foetus of Fourteen Weeks=

By G. J. Romanes

School of Anatomy, Cambridge

==Introduction==

The cell columns of both normal and abnormal human spinal cords have been described by many authors, but this literature does not include many examples of early foetal stages. Researches which have been carried out by the present author to determine the development of the cell columns in the cervical region of the spinal cord of the rabbit have shown that at certain stages in their development the cell columns are much more distinct than in the adult animal. This is particularly true of the early foetal stages in the rabbit. In the case of this mammal no evidence has been found to confirm the statement of Angulo y Gonzalez, with reference to the white rat, that the cell columns are more numerous and complex in the newborn than in the adult, but he has probably come to this conclusion because of the difficulty of determining the cell columns in the adult as compared with the earlier stages when they are much more compact and discrete. It seemed of interest, therefore, to determine the cell columns in the cervical and lumbar enlargements of the spinal cord of a well-fixed human foetus of fourteen weeks, for this might give a clearer picture of them than the later stages.

==Methods==

The spinal cord was removed, together with the roots and ganglia, after fixation in 10 % formalin, but, since this fixative does not allow satisfactory staining with toluidin blue in the case of embryos and foetuses, the cord was again fixed in acid alcohol (which has been found to improve the staining properties of the nerve cells in the spinal cord of embryos fixed in formalin). The cord was then dehydrated, embedded in paraffin wax and serially sectioned at 15 p.. The sections, mounted. on slides, were first stained with toluidin blue. This series was carefully studied and serial drawings and photomicrographs made to show the main cell columns in the spinal cord. The sections were then destained, and restained by the Bodian lprotargol method to show the fibres with a View to determining if possible the connexions of the cells in some of the columns, and to make certain that none of the divisions described in the toluidin blue series was due simply to the passage of a bundle of fibres through a cell column.

==Nomenclature==

The columns in each of the cervical and lumbar series are numbered in order of their appearance when the series is traced caudally from the cephalic part of the enlargement. No names have been used to designate the cell columns of the enlargements, for, although this method has the advantage of describing the position of a cell group, it becomes too complicated when the number of groups increases beyond five or six. From this it will be seen that the numbers given do not necessarily correspond with the numbers used by other authors; identical numbers might cause homologies to be drawn between cell columns of the same anatomical position though not necessarily of similar function in different animals.‘

==The Cervical Enlargement==

(Text-fig. 1; Pl. 1, fig. 1)

In the lower part of the third cervical segmentl there exist four cell columns which have been numbered from medial to lateral 1, 2, 3 and 4. Column 1 lies at the anteromedial aspect of the anterior horn -with column 2 situated just posterior to it and in some sections fused with it. Column 3 lies at the anterolateral edge of the anterior horn just lateral to column 2, while just posterolateral to this is column 4. Traced caudally, columns 1 and 2 become completely fused in the fifth cervical segment, and the fused mass, consisting mainly of cells of column 1, remains in the same position throughout the cervical enlargement.

Column 3, traced caudally, retains the position described above till, passing medially in the eighth cervical segment, it fuses with the anterior surface of column 8 forming an anterior column which, decreasing in size, inclines medially in the first thoracic segment towards column 1, on whose lateral aspect it enters the upper part of the thoracic spinal cord.

Column 4, which lies posterior to column 3 in the fourth cervical segment, expands in a posterior direction throughout the fifth, finally dividing into a dorsal and a ventral part in the sixth. The dorsal part, column 7, is only present throughout the latter segment and becomes fused in its caudal part with column 4 which, extending down into the eighth cervical segment, again divides into anterior (column 4) and posterior (column 10) parts. The former fades out in the upper part of the first thoracic segment, having maintained a posterolateral position throughout. Column 5, which appears posterior to column 4 in the upper part of the fifth cervical segment, rapidly divides into posterolateral (column 6) and anteromedial (column 5) parts. The latter passing anteromedially to take up a central position in the sixth cervical segment is continued caudally in this situation and disappears in the upper part of the seventh. Column 6 rapidly increases in size throughout the fifth and sixth cervical segments and is situated here posterior to columns 4 and 7. It disappears in the upper part of the eighth cervical segment where column 9 overlaps the posterior part of its caudal extremity. Column 8 appears medial to column 4 close to the caudal end of column 5. From this central position in the seventh cervical segment it inclines anteriorly to unite with the posterior surface of column 3 in the eighth cervical segment.


* Unfortunately the first three cervical segments are missing from the spinal cord, these having been removed with the head for a previous study. 


Column 9, which is the most posteriorly situated cell column of the anterior horn from the eighth cervical to the upper part of the second thoracic segment,

Text-fig. 1. A diagram to show the relative positions of the cell columns of the cervical enlargement of the spinal cord of a 14-week human foetus. Where more than one drawing of a particular segment is made the first drawing shown is the most cephalic in this figure and in Text-fig. 2.

is single in its cephalic part but, after considerable expansion, becomes divisible into subsidiary columns from the first» thoracic segment caudally. These subsidiary columns are irregularly fused and are therefore considered to be divisions of column 9 rather than separate cell columns. Four parts of this cell column are visible in the first thoracic segment: three (9 a, 9b, 9c) lie at the lateral edge of the column, one behind the other, so that 9a is the most posterior, while the fourth (9 d), situated medial to them, lies posterior to column 10. Further caudally a fifth part (9 e), lying anterior to 9d and medial to 9c, is occasionally present. Of these divisions only columns 9a and 9b extend into the upper part of the second thoracic segment, 9c, 9d and 9e having disappeared in the lower part of the first thoracic segment.

Column 10, situated at the lateral edge of the anterior horn in the eighth cervical segment between column 4 anteriorly and column 9 posteriorly, extends further caudally than column 4, ending in the upper part of the first thoracic segment posterior to column 3.

The cervical enlargement thus consists of ten cell columns of which only two are continued down into the thoracic spinal cord. Of these ten cell columns column 9 is the largest and most complex; it is situated most posteriorly and passes further caudally than any other cell column of the cervical enlargement, its caudal part coming into relation with the cephalic part of the intermediolateral cell column of the thoracic spinal cord. This column 9 reaches its maximum degree of differentiation in the first thoracic segment.

There is much evidence to suggest that the most posterior cell column of the lateral part of the anterior horn in the caudal extremity of the cervical and lumbar enlargements contains the cells of origin of the axons which supply the muscles of the hand or foot in man and other mammals (van Gehuchten & de Buck, 1898; van Gehuchten & Nelis, 1899; de Neef, 1901; Bok, 1928; Yu-Ch’i'1an Tsang, 1939), and in the cervical enlargement it is not surprising to find that this column is situated in the segment whose nerve supplies the muscles of the hand, and that the column itself shows a great degree of complexity which seems likely to be related to the degree of anatomical and functional differentiation of the hand in man. (It is of interest that the lateral extension of the anterior horn, due to the presence of this column, is greater in man than in the anthropoid apes; Kappers et al. 1936.)


Sections stained by the Bodian technique show the same columnar structure as the toluidin blue sections. This method shows that fibres passing to the spinal accessory nerve arise from the dorsal part of column 4.« cephalic to the appearance of column 5 and from column 5 in the more caudal part. It seems possible that this is all one column and that column 5 is merely a disconnected portion of column 4.

==The Lumbar Enlargement==

(Text-fig. 2; Pl. 1, fig. 2)

In the lower thoracic region a mass of cells situated at the anterior part of the anterior horn can be divided into anterior, central and anterolateral groups all of which are intimately connected with each other. In the upper lumbar region the central and anterolateral groups disappear but the anterior group is carried caudally into the lumbar enlargement and is called column 1. 



Column 1, Which is a small group of cells, retains the position described above throughout the lumbar region but decreases in size and disappears in the first sacral segment; it reappears in the third and again disappears in the fifth. Column 2, arising in an anterolateral position in the second lumbar segment,

Text-fig. 2. A diagram to show the relative positions of the cell columns of the lumbar enlargement of the spinal cord of a 14-week human foetus.

increases rapidly in size becoming divisible into anterior _(column 2) and posterior (column 3) parts, which continue caudally close together in, a similar position and coalesce in the fifth lumbar segment. From this position the single column extends into the third sacral segment where it disappears. Throughout its length column 2 is characterized by the presence of a bundle of longitudinal fibres running in its substance.


Column 4, appearing as a cap of cells over the posterior aspect of column 3 in the third lumbar segment, expands medially and splits into a medial (column 5) and a lateral (column 4) part. The latter fades out in the middle of the fourth lumbar segment dorsal to column 3.


Column 5 sweeps further anteromedially to become central in position in the fourth lumbar segment, where it is divisible into an anterior and a posterior part by virtue of the presence of a longitudinal bundle of fibres lying among the cells of the posterior division. Fusion between these two parts takes place in the upper part of the second sacral segment where the column inclines laterally, coming to lie between columns 2 and 3 anteriorly and column 6 posteriorly close to the lateral edge of the anterior horn. It disappears in the upper part of the third sacral segment in this position.


Column 6 appears in the lower part of the fifth lumbar segment posterior to columns 2 and 3 and situated at the lateral edge of the anterior horn. It increases in size throughout the first sacral segment and appears to be divisible into medial and lateral parts as it expands into the lateral white matter, causing a prominent bulge of the posterior part of the anterior horn. The lateral part which causes this expansion has been called column 7. These two columns, 6 and 7, are fused considerably throughout their length, and finally come together in the -caudal part of the first sacral segment where their fused mass is large and is separated from columns 2 and 3 by the caudal part of column 5. With the loss of this latter column the two groups, formed from the fused columns 2 and 3 and the fused columns 6 and '7 , come into contact; and, with the loss of the former in the third sacral segment, columns 6 and 7 become anterolateral in position and fade out just caudal to columns 2 and 3, except for a small part which is continued further caudally anterior to column 8 and disappears just before it.


Column 8 starts as a small mass of cells just posterior and slightly lateral to column 7 in the second sacral segment. It increases rapidly in size and is large throughout the third sacral segment, but is rapidly lost in the upper part of the fourth. It is the most posterior cell column of the lateral part of the anterior horn.


Thus it will be seen that there are eight cell columns in the lumbar enlargement and that their arrangement is in many ways similar to that found in the cervical enlargement. For example the most posterior column appears at the caudal extremity of each enlargement and extends further caudally than any other cell column in it. Also in each case there is a central column, column 5, which appears at the lateral edge of the anterior horn and, passing caudally, takes up a central position. The central column of the lumbar enlargement is much larger than that of the cervical region, and this is also true for all of the other columns of the lumbar enlargement with the exception of column 8, which is considerably smaller than its counterpart in the cervical region. It is possible that this difference in the size of the cell columns of the two enlarge ~ ments (cf. Pl. 1, figs. 1, 2) is directly related to the amount of peripheral mesoderm innervated by the cells in the columns. Again columns 3 and 4 of the cervical region are similar in position and relations to the columns 2 and 3 of the lumbar region, though the latter are more frequently fused than the former.

The general similarity between the arrangement of the cell columns of the two enlargements in mammals has already been noted by various workers, notably de Neef (1901), and it has been shown that similarly situated groups in the two enlargements supply analogous segments of the limbs (de Neef, 1901; Bok, 1928; etc.), the more anterior and cephalic cell columns supplying the proximal segments and the more posterior and caudal columns the distal segments of the limb (van Gehuchten & de Buck, 1898; Van Gehuchten & N elis, 1899; de Neef, 1901; Bok, 1928). During research on the development of these cell groupings the author has found them to be developed as a direct result of the connexion of the cells with the segments of the limb which they supply, thus suggesting that similar limbs are likely to have similarly arranged cell columns supplying them.


Van Gehuchten & Nelis (1899) described a posteriorly situated column in the lumbar enlargement as the nucleus of supply of the foot muscles. Since this is similar in position to column 8 it seems probable that the latter is functionally similar, and it is not surprising to find that this column is not so complex as its counterpart in the cervical region. This may probably be correlated with the small range of functional activity of the foot as compared with the hand.


On account of its position and its presence throughout the spinal cord, column 1 of both enlargements is probably a nucleus of supply of the trunk musculature, and it is especially large and divisible into two parts in the upper cervical region, so giving rise to column 2. The close relation of the latter to column 1 suggests a similar function, and its presence in the lower part of the third and throughout the fourth cervical segments makes it possible that column 2 is the phrenic column. This conclusion is borne out by Bruce (1901) who describes a similarly situated column as the nucleus of the phrenic nerve. Column 5 of the cervical region has been shown to supply the spinal accessory nerve and it extends to the caudal limit of this nerve, though Bruce (1901) states that the accessory nucleus ends in the fourth cervical segment.


When the columns described above are compared with the results obtained by other observers on adult material it is seen that there is considerable agreement as regards the number and position of the cell columns present. Though the classical work of Bruce (1901) does not name as many columns as are described here, he admits the subdivision of several of his columns to make up a like number. Very similar results have been obtained by J acobsohn (1908) for the cervical and lumbar regions and by van Gehuchten & de N eef (1900) for the lumbar region only. Thus it seems probable that as early as the fourteenth week of foetal life the cell columns have attained an adult arrangement.


==Summary==

The cell columns in the cervical and lumbar enlargements of a human foetus are described and compared and several points of similarity are shown. The cell columns are already adult in their arrangement by the fourteenth Week of foetal life.

==References==

Box, S. T. (1928). W. v. M<'51lendorﬂ"s Handbuch der milcroslcopischen Anatomie des M enschen, 4/1, 478.

BRUCE, A. (1901). A Topographical Atlas of the Spinal Cord. London.

VAN GEHUCHTEN, A. & DE BUCK (1898). J. N eurol., Brux. Quoted from van Gehuchten, Systéme nerveux, Louvain. ' ’

VAN GEHUCHTEN, A. & DE NEEF, C. (1900). N évraxe, 1, 201. Quoted from Systéme nerveux.

VAN GEHUCHTEN, A. & NELIS (1899). J. N eurol., Brux. Quoted from Systéme nerveux.

JAooBs0HN, L. (1908). U ber die Kerne des menschlichen Ritclcenmarlcs. Berlin.

KAPPERS, C. U. A., HUBER, G. C. & CROSBY, E. C. (1936). Comparative Anatomy of the Central Nervous System of Vertebrates. New York.

DE NEEF, C. (1901). Névraxe, 2, 71.

YU-C11’I"IAN TSANG (1939). J. comp. Neurol. 70, 1.

==Explanation of Plate 1==

fig. 1. Transverse section through the fifth cervical segment of the spinal cord of a human foetus of fourteen weeks. ‘Stain, toluidin blue. x 70.

fig. 2. Transverse section through the second sacral segment of the spinal cord of a human foetus of fourteen weeks. Stain, toluidin blue. x 70. 





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