Book - Manual of Human Embryology 15

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Keibel F. and Mall FP. Manual of Human Embryology II. (1912) J. B. Lippincott Company, Philadelphia.

Manual of Human Embryology II: Nervous System | Chromaffin Organs and Suprarenal Bodies | Sense-Organs | Digestive Tract and Respiration | Vascular System | Urinogenital Organs | Figures 2 | Manual of Human Embryology 1 | Figures 1 | Manual of Human Embryology 2 | Figures 2 | Franz Keibel | Franklin Mall | Embryology History

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XV. The Development of the Chromaffin Organs and of the Suprarenal Bodies

Chromaffin tissue is to be assigned to the group of organs producing internal secretion. It secretes a substance which produces contraction of the non-striped musculature and whose principal function seems to be to maintain the blood-pressure and the vascular tonus at corresponding levels. That the increased bloodpressure produced by suprarenal extract is due to the chromaffin medullary substance of the glands has been definitely proved by A. Biedl and J. Wiesel, who worked with the purely chromaffin aortic bodies of man. The chrome reaction must depend on a coloring of the secretion,- for it fails, as Schur and Wiesel have shown, when the adrenalin is exhausted.

The anlagen of the chromaffin tissue, including that of the medullary substance of the suprarenal glands, are primarily associated with the cells from which the sympathetic bodies are formed. This has led many authors to assume a genetic connection between the two kinds of tissue and to derive the chromaffin tissues from sympathetic cells, although only those cells which really form portions of the sympathetic system should be termed sympathetic cells.

The anlagen of the sympathetic and chromaffin tissue consist of an apparently uniform matrix composed of deeply staining cells, which measure 4-6^ and which form what may be termed sympatho-cJiromafftn tissue. The uniformity of the elements is especially striking when one compares a mass of purely sympathetic cells (sympathoblasts) with the cell masses which have wandered into the suprarenal glands but have not yet become differentiated, as they will later entirely or for the most part, into the cells of the medullary portion of the glands (chromaffinoblasts). It becomes clear in such cases, and especially in those in which the chromaffin bodies prevail, that one can only properly speak of sympathetic ganglia when the anlagen of the two kinds of tissue have become differentiated from one another.

As to the genetic character of the chromaffin bodies there has been no unanimity. While F. Leydig, F. M. Balfour, E. Griacomini, and E. Grynfeltt declared in favor of an epithelial nature and a secretory function for the chromaffin cells, others inclined toward the belief that they were either nervous elements or closely related to these. According to S. Meyer the chromaffin cell-nests of the Batrachia constitute a tissue sui generis, which appertains to the nerve tissues and whose function is to provide for the new formation of nerve-fibres. H. Eabl regarded the medullary cells of the suprarenal glands as undeveloped sympathetic ganglioncells, C. K. Hoffmann described them as sympathetic nerve-cells of peculiar form, and V. Diamare looked upon the chromaffin cells as epithelial cells of nervous origin. A. Kohn at first accepted the view that the chromaffin cells, on account of their origin and final relations, belonged to the sympathetic system. He emphasized the high degree of relationship existing between the chromaffin and the sympathetic cells, but later protested, "on general and special grounds and on principle, against the inclusion of the chromaffin cells among the secretory epithelial cells ; ' ' further, he pointed out their difference from the nerve-cells, and, finally, regarded them as elements of a peculiar type of tissue. It is true that all the peculiarities of the chromaffin tissue do not without modification harmonize with the definition which the textbooks give for epithelial tissue, but, on the other hand, many of our definitions are made before there has been a collation of all the facts necessary for the framing of a definition correct in all details. None of the characters which distinguish chromaffin tissue, such as the abundance of nerves in it, the occurrence of scattered chromaffin cells, and its relations to the sympathetic system, actually exclude it from classification as an epithelial tissue, and yet, as regards especially the last-named character, the relation is merely a topical one and no indication of a common genetic derivation from the ectoderm. One might, of course, advance in favor of this idea the suggestion that the chromaffin cells are derived from other than sympathetic formative cells, but, on the other hand, it may be pointed out that the identity of the elements contained in sympatho-chromaffin tissue need be no reason for deriving the chromaffin cells from the sympathetic ones. On the principle a potiori fit denominatio the authors, in accordance with their erroneous conception, must derive the sympathetic ganglia of the plexus cceliacus from the neighboring chromaffin bodies. One can only agree with the remark of A. H. Soulie that the chromaffin cells are structures in juxtaposition with the sympathicus and need not be regarded as nerve-cells nor as derivatives of these. Their function, which should also be taken into consideration in determining the character of a tissue, speaks distinctly as to their glandular nature.

The differentiation of the sympathoblasts and chromaffinoblasts (parasympathetic formative cells) becomes evident rather late. After their separation is complete the anlagen of the two kinds of tissue are sharply separated: the chromaffin formative cells are, for instance, larger and do not stain as intensely as the small sympathoblasts, which still adhere to the sympathochromaffin type. Furthermore the differentiation appears to bring about a definite separation of the chromaffin and sympathetic elements, for no commingling of the two kinds of cells is to be observed. The occurrence of individual sympathetic cells in the free chromaffin bodies and of individual chromaffin cells in sympathetic ganglia must be regarded as exceptions to the rule. Whether the parasympathetic cells show the chrome reaction at this stage of development is yet to be determined.

In later stages the development of the chromaffin tissue precedes that of the sympathetic. In this connection it may be noted that in the ganglia of the abdominal plexuses extensive parasympathetic bodies are differentiated at a time when the sympathetic formative cells have not yet altered from the original sympathochromaffin type (fetus of 6 cm.). The statement of Soulie that the parasympathetic cells first develop at a time when neuroblasts are present in the sympathetic ganglia is incorrect as a general statement; it can, at all events, be accepted only as referring to the medulla of the suprarenal glands, which, as is known, is late in differentiating.

The chromaffin bodies of the gangliated cord are in general rounded masses, which usually lie in depressions in the dorsal portions of the ganglia (Fig. 106, ch). According to A. Kohn they appear later than those of the abdominal plexuses and their appearance does not seem to occur at a definite time, for they are lacking, for example, in an embryo of 28 mm. (in the gangliated cord) completely. They vary in size; exceptionally large bodies occur alongside of small ones. In the new-born child they reach a length of 1.0-1.5 mm. and not infrequently lie entirely or half way outside the capsule of the sympathetic ganglion (Fig. 107). They also vary in number; sometimes individual ganglia have several chromaffin bodies ; for example, a ganglionic mass extending from the first to the fourth rib had ten, in another case a ganglion of the abdominal portion of the cord had four, and in still another case six chromaffin bodies occurred in connection with four ganglia of the abdominal portion of the cord.

The chromaffin bodies of the ganglia of the cord are equivalent to the suprarenal bodies of the Selachians, and it is certainly noteworthy that, as a comparative study shows, so far as these bodies are concerned there is a complete continuity from the cartilaginous fishes up to man. F. Leydig first suggested the occurrence of organs in the mammalia that might be regarded as homologous with the suprarenal bodies of the Selachians. He started, it is true, with an assumption that has since been given up, — namely, that the suprarenal bodies merely represented the medullary substance of the mammalian suprarenal gland broken up into many portions; but his remark, "or perhaps also here (i.e., in the mammals) adequate investigation may reveal in the individual ganglia of the gangliated cord portions that repeat in petto the suprarenal bodies," shows that Leydig did not oppose the possibility that in mammals, in addition to the medulla of the suprarenal glands, other chromaffin tissue might also be present in the gangliated cord.

Fig. 106. — Horizontal section through a vertebra (v) and a ganglion of the gangliated cord (gr) in a fetus of 6 cm. X70. a, aorta; ch, chromaffin body of the ganglion; n, splanchnic nerve; pi, pleura; r, rib; v, vertebra.

The chromaffin bodies of the ganglia of the sympathetic cord should alone be termed suprarenal organs. Statements to the effect that the suprarenal bodies correspond to the medulla of the suprarenal glands of the higher vertebrates should no longer be made, least of all in text-books. The inaccuracy of such a statement becomes apparent when one considers that in the mammalia, in addition to its occurrence in the medulla of the suprarenal glands, chromaffin tissue is also associated with the ganglia of the sympathetic gangliated cord.

Chromaffin Bodies in the Ganglia of the Abdominal Sympathetic Plexuses. — These bodies may occur wherever there are sympathetic ganglia. That they occur, as R. Wiedersheim states, "in all organs which are termed glands with internal secretion" is incorrect. In certain plexuses (plexus intercaroticus, coeliacus, suprarenalis, renalis, aorticus, and hypogastricus) they are of constant occurrence; in others (plexus cardiacus, according to Wiesel, and plexus mesentericus inferior) they are inconstant.

Fiq. 107. — Horizontal section through an intercostal space in a new-born child. X85. Chromaffin body (.ch) situated outside the capsule of a ganglion {gr) of the sympathetic cord.

Of organs in connection with which they occur there may be mentioned the kidneys (surface and sinus renalis), the ureter, the pelvis of the kidneys, the surface of the suprarenal glands, the accessory suprarenal glands, the prostate, the paroophoron (Aschoff, A. Rielander), the epididymis (Aschoff), the ovary (Bucura), and the retroperitoneal Pacinian corpuscles. Cell masses in the caudal sympathetic ganglia of a Dasypus fetus of 8 cm. seem to indicate that chromaffin bodies may also develop in the caudal portion of the sympathetic cord. 1 They are lacking, so far as is known, in the ganglia associated with the branches of the trigeminus. The coccygeal gland has been erroneously assigned to the chromaffin system.

1 The cell masses were not situated in the ganglia of the caudal portion of the sympathetic cord, but in ganglia of the caudal arterial plexus. Vol. II.— 11

The glandula intercarotica is associated with the plexus intercaroticus. That it belongs to the chromaffin system was recognized by H. Stilling. Before his time this organ had variously been identified as a sympathetic ganglion (Andersch), a nerve gland (H. von Luschka), a vascular structure (J. Arnold), a derivative of the branchial arches (K. Stieda, C. Rabl, Maurer), and, finally, as a derivative of the adventitia of the internal carotid artery (Kastschenko, Marchand, R. Paltauf). According to Paltauf, with whose statements those of Kastschenko and Marchand essentially agree, the carotid gland develops "in man and other animals, and therefore probably in the mammalia in general, without any epithelial anlage from a circumscribed growth of the wall of the internal carotid. ' ' Any attempt to derive this gland from a branchial pouch or from a thickening of the wall of a vessel must fail, since chromaffin cells can only be produced from sympatho-chromaffin tissue. What significance the indistinct thickening of the wall of the internal carotid possesses is yet to be determined; that it represents a structure independent of the anlage of the carotid gland is shown, as A. Kohn points out, by the fact that the thickening can also be observed in those cases in which the gland is situated nearer to the external than the internal carotid (as in the dog). It may further be remarked that nowhere else have similar thickenings of the adventitia of arteries been observed in the neighborhood of chromaffin bodies.

A. Kohn derives the chromaffin elements of the glandula intercarotica from the nerve anlage which passes from the upper cervical sympathetic ganglion between the two carotids. In a 44 mm. pig embryo he finds in this plexus ganglion-cells, some of which have a large and feebly staining nucleus, and believes that these latter cells represent the specific elements of the carotid gland.

Up to the present only scattered observations have been made on the development of the glandula intercarotica in man. R. Paltauf investigated an embryo of 15 mm. and a fetus of 45 mm.; in the former the gland had not yet appeared ; it was present in the latter, but the thickening of the internal carotid artery mentioned above was also present. (According to Kohn the cells of the anlage of the gland in a 19 mm. (NL) embryo resemble neither the small, deeply staining ganglion-cells of the intercarotid plexus nor the chromaffin cells.) In Fig. 108 the anlage of a carotid gland of a 193/4 mm. embryo is shown. The plexus intercaroticus contains richly vascular masses of small cells, which follow the course of the nerves descending from the superior cervical ganglion and are connected with the cells of the ganglion. The process that extends from the ganglion to the plexus intercaroticus on the medial side of the internal carotid consists apparently of sympatho-chromamn tissue, and also furnishes the material for the specific cells of the carotid gland. In a 28 mm. embryo the differentiation of the parasympathetic cells is already accomplished.

Chromaffin Bodies in the Abdominal Plexuses. — In the abdominal sympathetic plexuses the sympatho-chromamn tissue separates into an extensive ventral parasympathetic and a much weaker dorsal sympathetic layer; the latter at places also bounds the former laterally. The two kinds of tissue, accordingly, very early arrange themselves in the abdominal plexuses in the manner characteristic of the adult condition (Fig. 109). The youngest embryo with differentiated chromaffin bodies has a length of 18-19 mm. Before this stage sympatho-chromaffin tissue occurs everywhere in the places later occupied by the abdominal sympathetic plexuses and is especially abundant in the region between the two suprarenal glands (plexus coeliacus and suprarenalis) and in front of the aorta (Fig. 110). Here it pushes its way between the aorta and the left renal vein and extends downward to below the origin of the inferior mesenteric artery. These masses are mainly destined for the formation of the two extensive aortic bodies (com pare Fig. 110 with Fig. 109). In an 18 mm. embryo there are already present on either side two chromaffin bodies, an upper, smaller one above the renal vein and a lower, larger one (aortic body) caudad to this vein. These two bodies extend from the 21st vertebra to in front of the 24th, or on the left side to the disk between the 23d and 24th vertebrae. The vascular connective tissue trabecular in the interior of the body, whose meshes the cellcords occupy, are already plainly distinguishable in a 19.5 mm. embryo, and in a well-preserved 19 mm. embryo the differentiation of the sympathetic and chromaffin tissues has just begun (Fig. 109). This is at first shown by the cells in the chromaffin bodies (r and I) becoming in places less closely packed together than they are in the sympathetic ganglia (g). It seems that the development of a vascular connective tissue, which divides the cell-masses into cords, permits of a looser texture in the bodies.

Fig. 108. — Horizontal section through the anlage of the carotid gland (gl. i.) in a 19.7 mm. embryo. X100. c.i., internal carotid artery; h, pharyngeal cavity; ph, wall of 'pharynx; I, larynx; 8, superior cervical ganglion; 10, ganglion nodosum of the vagus; the white spaces represent cervical veins.

Fig. 109. — Horizontal section through the sympatho-chromafiin anlage of the aortic bodies (r and l) and through the aortic plexus (g) in an embryo of 19 mm. a, aorta; gr, gangliated cord; m, mesentery; u, ureter; v, vertebra.

In the section figured the chromaffin bodies are separated from the ganglia of the plexus by a cleft (see Fig. 109). This is apparently an artefact due to the knife.

In the course of the further development new chromaffin bodies are added to those already present, so that in all from seven to twenty-six or even more — in one case nearly seventy — of these bodies may be counted. An increase in the number may also occur by several small bodies developing in place of a single large one.

The largest of all are the aortic bodies (Fig. Ill, r and I) ; their cranial ends lie at the origin of the superior mesenteric artery or at those of the renal arteries, and their lower ends are situated at the level of the division of the aorta (on the right side) or immediately above this (on the left side). The two bodies lie at the sides of the inferior mesenteric artery and their lateral borders may be in contact with the kidneys and the ureters. In fetuses of 4-5 cm. their length is over 1 mm. ; in new-born children the average length of the right one is 11.6 mm. and that of the left one 8.8 mm. The upper ends of the bodies are frequently (14.8 per cent, in new-born children) united by a connecting bridge (isthmus, Fig. Ill, i), which lies over the aorta below the superior mesenteric artery. When the isthmus is wanting the upper end of the right body sometimes becomes much broadened and a division of the parenchyma into two portions is indicated by a connectivetissue septum (Fig. Ill, D). In connection with the hypogastric plexus four chromaffin bodies (two on each side) are usually developed ; their number may be increased up to seven.

Fig. 110. — Horizontal section through sympatho-chromaffin anlage of the aortic bodies and the aortic plexus (a. ch.) in an embryo of 14.5 mm. X50. a, aorta; g, reproductive gland; m, mesentery; n, kidney; w, mesonephros; v, vertebra.

Fig. 111. — Chromaffin bodies of the abdominal plexuses. An explanation of the lettering will be found inlthe table on p. 167.

Above the aortic bodies other cranial chromaffin bodies occur, either independent or branching off from the isthmus and lying on the plexus coeliacus and plexus suprarenalis. Most frequently there is a large body on each side on the medial border of the suprarenal gland (Fig. Ill, A and B). These bodies may be prolonged downward for some distance, lateral to the isthmus; they are not infrequently of considerable thickness (Fig. 112) and may be divided into two portions along their anteroposterior diameters. It may also happen that two lateral bodies are formed on each side, in which case one lies in front of the aorta and the other on the suprarenal gland (Fig. Ill, B). Occasionally, in addition to the lateral bodies a median one also branches off from the isthmus and extends in front of the aorta up to the origin of the superior mesenteric artery.

Fig. 112. — Horizontal section through the aortic bodies of Fig. Ill, D, passing through the process /'. From a 23 mm. embryo. X40. r and I, right and left aortic bodies; a, aorta; gr, gangliated cord; to, mesentery; n, suprarenal gland; r, kidney; v, vertebra. The darkly stippled areas in the neighborhood of the aortic bodies represent anlagen of the sympathetic ganglia.

Fig. 113. — Horizontal section through the chromaffin bodies a, i, b, c, and I of Fig. Ill, D. From a 23 mm. embryo. X 40. o, aorta; gr, gangliated cord; re, suprarenal gland; r, kidney; v, vertebra. The darkly stippled areas in the neighborhood of the chromaffin bodies represent anlagen of plexus ganglia.

The fact that the chromaffin bodies of the plexuses send off processes or branch, brings it about that the same body may be cut several times, so that in the study of sections more bodies may seem to be present than is actually the case (compare Figs. Ill, D, and 113).

Fig. 114. — Horizontal section through the chromaffin aortic body of a new-born child (Bielscliow.^ky's , stain). X200.

The size of the chromaffin bodies in relation to the neighboring organs may be seen from Figs. 112 and 113. Compare, for instance, the aortic bodies or the isthmus with the aorta.

In the new-born child the chromaffin bodies of the plexuses have a smooth, light-brown surface; the capsule sends numerous processes into the interior, which primarily bound the cell cords (Fig. 114). The vascular system is richly developed in them.

The chromaffin bodies of the plexuses are in no way homologous with the suprarenal bodies, even although they are identical in structure. There is, of course, correspondence between the two kinds of bodies in so far that all chromaffin bodies are derived from sympatho-chromaffin tissue, but the topographical factor must not be neglected to the extent of identifying, without further evidence than this, bodies that occur in association with the gangliated cord with others that occur in the ganglia of the plexuses.

In the post-fetal periods of life the chromaffin bodies present signs of degeneration without actually disappearing. In adults the aortic bodies can no longer be perceived by the naked eye, although microscopic investigation will reveal the presence of chromaffin tissue in the regions formerly occupied by them. Thus it was not possible to dissect out the aortic bodies in the body of an individual of 39 years of age, but microscopic investigation showed the presence of' chromaffin bodies, 1.5 cm. in length but poor in parenchyma, in the sympathetic trunks running on either side of the inferior mesenteric artery in front of the aorta. Similar observations were made upon a child of nine years and a youth of nineteen ; but in these two cases, as well as in that of a youth of fifteen with well-preserved aortic bodies and a child of two years whose aortic bodies were poor in parenchyma and showed signs of hyaline degeneration, the bodies under consideration could be detected macroscopically.

Fig. 115. — Horizontal section through the isthmus (i) of the aortic bodies of an embryo of 60 mm. a, aorta; ch, chromaffin body on the pelvis of the kidney (on the left side) and in front of a branch of the renal artery (on the right side); g, anlagen of plexus ganglia; gr, gangliated cord; r, kidney; P. r, pelvis of kidney; v, vertebra.

The Suprarenal Gland

The suprarenal glands are composed of two substances, the cortex and the medulla, differing in their structure and development. The former is derived from the ccelom epithelium, the latter from the sympatho-chromaffin tissue. The cortical cells appear before those of the medulla and the cortex is already a relatively large body before it receives the anlage of the medulla. The embryonic suprarenal glands of man and also of the other mammals resemble for some time the interrenal bodies of the Selachians, which, as is known, are composed throughout life of cortical substance only.

A. H: Soulie finds the first traces of the suprarenal glands in an embryo of 6 mm., and in correspondence with this Poll correctly assigns their appearance to the beginning of the fourth week of development. The anlage of the organ, according to Soulie, takes the form of buds composed of cells which project from both sides of the root of the mesentery into the mesoderm situated ventral to the aorta. In a 6.5 mm. embryo of my collection the region of the future suprarenal gland is indicated by mitoses in the ccelomic epithelium, and beneath the epithelium formative cells are closely aggregated, although they do not yet show the characteristics of the cortical cells. In an 8 mm. embryo the glands are already definite organs, completely separated from the coelom epithelium. With this the observations recorded in the Normentafel of Keibel and Elze agree. In a 9 mm. embryo the suprarenal glands are already vascularized, but the central vein becomes visible only later (according to the material at my disposal only in an embryo of 23 mm.).

In young embryos the suprarenal cortex is composed of elements that are larger than the sympatho-chromamn cells and stain readily when treated with the ordinary staining reagents. The connective-tissue capsule of the organ has a somewhat looser texture on the medial than is the case on the lateral surface, a condition that has some importance in connection with the immigration of the synrpatho-chromanin tissue.

The siiprarenal glands that have separated from the coelom epithelium in embryos of from 8 mm. to 12 mm. lie on either side in a projection of the posterior wall of the coelom (the suprarenal ridge) which is situated medial to the mesonephros, that is to say, between this and the mesentery, and is continued cranially, without any distinct delimitation, into the dorsal portion of the pleuroperitoneal membrane (the dorsal pillar of the diaphragm), a portion of the gland projecting into this pillar. The suprarenal ridge and the pleuroperitoneal membrane are separated from the mesonephros by a groove. 2 In an embryo of 11 mm. in the region of the stomach and the caudal extremity of the lungs the suprarenal ridges have united by means of a fold (the caudal limiting fold of Hochstetter) with the dorsal surface of the liver on the right side and on the left with the junction of the stomach and oesophagus. The caudal limiting fold, which separates the caudal portion of the pulmonaryniche from the lateral portion of the abdominal cavity, has the same relations in man as in other mammals. A comparison of a horizontal section through this fold in a human embryo of 11 mm. with a similar section of a 10 mm. cat embryo shows almost exact correspondence. In Hochstetter 's figure of a horizontal section through the fold in a 10.2 mm. cat embryo the suprarenal gland, it is true, is not shown, but, as I have convinced myself, the dorsal half of the fold is given off from the suprarenal gland also in the cat.

3 Similar relations occur in animals, the differences being only those of detail. Thus, for example, in an 11 mm. cat embryo the suprarenal ridge does not project as much as in man and is not separated from the mesonephros by a groove.

Fig. 116. — Horizontal section through the suprarenal gland (n) of a 17 mm. embryo. X60. a, aorta; gr, gangliated cord; m, mesentery; n. spl., splanchnic nerve; p, pleuroperitoneal cushion; v, vertebra. The darkly stippled masses, traversed by nerves, lying on the medial side of the suprarenal glands and sending processes into their substance, are sympatho-chromaffin tissue.

The posterior surface of the gland rests upon a coarsely meshed, almost (edematous, pleuroperitoneal cushion (the tissu muqueux lache peripleural of Brachet), which, as in animals, projects extensively behind the thoracic portions of the cardinal veins (Fig. 116). In embryos of 14 mm. and 15 mm. this cushion has an extensive development, while in an embryo of 28 mm. it has already undergone a great amount of retrogression. The mesonephros and the suprarenal ridges are also attached to the cushion.

The medulla of the glands is formed by the migration of masses of sympatho-chromaffin cells from the medial side toward the centre of the organ, so that they surround the central vein as the anlage of the medullary nucleus. In no preparations could the immigration of parasympathetic cells be observed, to say nothing of fully differentiated medullary cells. The elements of the migrating cell masses, which are entirely or for the most part composed of chromaffin formative cells, are sharply distinguished from the neighboring cortical cells by their, smallness and their intense stain (Fig. 118, s. ch.). It is conceivable that their migration," the cause of which has not yet been explained, may be inhibited and that the primitive form of the glands may exceptionally persist even in man.

Fig. 117. — Horizontal section through the region of the suprarenal glands in an embryo of 15 mm. X50. o, aorta; f, process of the suprarenal gland (n) that projects into the sympatho-chromaflBn tissue (represented by the darkly stippled masses medial to the gland); o, reproductive gland; m, mesentery; n. 8pl., splanchnic nerve; p, pleuroperitoneal cushion; Ur, mesonephros; v, vertebra.

The immigration of the sympatho-chromaffin tissue begins, as A. H. Soulie also finds, in embryos of about 19 mm. Processes of the adjacent sympatho-chromaffin tissue may, it is true, be observed penetrating and splitting up the medial portions of the glands even in embryos of 8 mm. (Fig. 116), and in some cases cortical processes (Fig. 117, /) or accessory suprarenal glands occur at an early stage in this region, but the immigration at these stages does not extend far beyond the region mentioned. 3

  • Cortical processes not infrequently persist and project by their free terminal portions into the neighboring nerve-plexus.

The association of the various cell masses to form the sympatho-chromaffin medullary nucleus of the glands does not take place until quite late. In embryos of from 6 cm. to 11 cm. (vertexbreech measurement) some masses have already reached the central vein, others, indicating that the immigration into the cortex is still continuing, have reached as far as the zona glomerulosa, and even in a fetus of 19 cm. the sympatho-chromaffin formative mass intended for the gland has not yet reached the centre of the organ. At first the central vein is surrounded by a continuous layer of sympatho-chromaffin tissue only at a circumscribed region. On the other hand, in an embryo whose suprarenal gland had reached a greatest length of 9 mm. the immigration of the medulla was completed and the extensive medullary nucleus surrounding the central vein already gave the chrome reaction. In view of these observations, the remark of R. Meyer that already in an embryo of 26 mm. the sympathetic cells had reached the centre of the organ seems scarcely reliable.

Fig. 118. — Section through the suprarenal gland of an embryo of 95 mm. (vertex-breech measurement), showing immigrated masses of sympatho-chromaffin cells (s. ch.). Some of these have already penetrated to the central vein.

The immigration of sympatho-chromaffin tissue into the gland seems to be continued even in post-fetal life, for J. Wiesel has found cell masses in the cortex even in new-born children.

In contrast with the fact that in an embryo of 19 cm. sympathochromaffin tissue still occupies the place of the medullary substance, it seems worthy of remark that occasionally in young fetuses (5-6 cm.), in addition to the wandering cell masses toward the centre of the gland, a circumscribed area of the medial surface together with the adjacent cortical layers is infiltrated with parasympathetic tissue. The circumstance that parasympathetic tissue is already developed in the region mentioned, while the adjoining cell masses destined to form the medulla have not yet passed beyond the stage of formative cells, indicates that it is a question of local parasympathetic infiltration.

Occasionally the path of the completed immigration is indicated by a process of the medulla, either simple or divided into several portions, which, directed toward the surface, either ends there or passes over into a neighboring chromaffin body (Fig. 119). A similar condition has been observed in various mammals, as, for instance, in the mouse by M. Inaba.

Fig. 119. — Sections through the medial portion of the suprarenal gland of a new-born child, a, accessory suprarenal; f, process of the suprarenal gland (n); v, veins. The chromaffin tissue and the medulla of the suprarenal gland in black.

The differentiation of the cortex into three layers takes place rather late. The zona glomerulosa is lacking even in the older fetuses, and according to 0. Scheel it is formed between the second and third year and only reaches the characteristic adult structure in the later years of childhood. The zona reticularis may be recognized in an embryo of 14.5 mm., and it would seem, as Gottschau and Mitsukuri have suggested, that its form is determined by that of the venous network, which, as is known, has an extensive development. The superficial layers of the cortex, even in older fetuses, are occupied by cells which, as A. Kohn has also pointed out. are smaller than the other cortical cells. They stain blue on treatment with hematoxylin and eosin, whereas the cells of the zona fasciculata and those of the zona reticularis take the eosin.

A. Boud, who stained the suprarenal of the mouse with eosin and toluidin, observed a similar reaction; he recognized a cyanophil zona glomerulosa as a younger form of the remaining eosinophil cortical cells.

The Development of the Accessory Suprarenal Glands

The majority of authors agree that the accessory suprarenal glands represent separated portions of the parent organ, and J. Wiesel succeeded in showing that the immigration of the sympatho-chromaffin tissue plays an important part in the separation. This immigration, that is to say, produces a cleavage of the medial surface of the suprarenal gland, as a result of which there is a separation of smaller or greater portions of the gland. This mode of development concerns, however, only those accessory suprarenal glands that occur in the region where the cleavage of the cortex by the sympatho-chromaffin tissue occurs.

The accessory glands either remain in the vicinity of the principal gland or they may eventually be situated far away from it if they become associated with organs that alter their position (accessory suprarenal glands on the spermatic vessels, in the ligamentum latum, and on the epididymis).

The accessory glands consist for the most part only of cortical substance, yet the fact that they occasionally also contain medullary substance shows that their separation is frequently due to the sympatho-chromaffin tissue. In fifty children that were examined with a view to determine the occurrence of accessory suprarenal glands, only one was found containing medullary substance. It was imbedded in the cceliac plexus, and one half of it consisted of a chromaffin body and the other half of cortex. A process of the suprarenal gland, similar to that represented in Fig. 119, B, f, had probably separated from the principal organ in this case. In other cases the chromaffin tissue migrates toward the centre of a cortical process, and thus there is formed later an accessory gland which is a diminutive copy of the principal organ. The accessory glands with medullary substance are accordingly divisible into two groups, those with peripheral and those with central medullary substance. Medulla and cortex may interpenetrate to such an extent that a process of the cortex or an accessory gland may consist of a thin cortical layer enclosing in addition to chromaffin tissue some scattered cortical trabeculse.

Accessory glands may also be formed in another way, namely, by portions being separated from the surface of the cortex in the region of the capsule, the general conditions remaining normal. To such separations are to be referred the nodular projections and spherical accessory glands that so frequently, even in large numbers, are to be found scattered over the surface of the suprarenal glands. They frequently imbed themselves in cavities in the organ and should not be confused with adenomata. Some of the nodes may come to lie in clefts in the neighboring sympathetic plexuses, and these show their origin from the superficial layer of the cortex by the fact that they are composed of zona glomerulosa alone. 0. Aichel recognizes still another mode of formation for the accessory glands, in deriving those associated with the reproductive organs from cross canals of the mesonephros that are in process of retrogression. This idea, however, is quite as erroneous as another of the same author, by which the accessory glands are identified with the suprarenal bodies.

A. H. Soulie also assigns the free chromaffin bodies to the category of accessory suprarenal glands. He seems to cling to the old idea that these bodies belong to the medullary substance of the suprarenal glands. The atrophy which they undergo later on is explained by their having no connection with the suprarenal gland with which they should be associated functionally. The incorrectness of this last supposition is shown by the fact that the chromaffin bodies do not atrophy in all mammals (for example, in Cavia cobaya), and in the Selachians an intimate relationship between the interrenal and suprarenal bodies does not really exist. Furthermore it may be pointed out that the anlage of the medullary substance is also originally free and lies outside the suprarenal glands. The primitive condition of the chromaffin bodies is represented by independent organs, entirely unconnected with the suprarenal glands, and for this very reason there are no grounds for terming the free chromaffin bodies accessory suprarenal glands.

Finally, it may be remarked, that the formation of accessory suprarenal glands from special buds of the ccelom epithelium is also conceivable, but up to the present there is no evidence that such a method occurs.


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