2. ESOPHAGO-SYMPATHETIC NERVOUS 

 SYSTEM 



The i>H'srnci' nf lU'ivo eolls in tlu' \v:ill nf tlir rs(i|ilKij;us was 

 first nu'iilidiu'il l)v l,(ioss {ISDIi) .•mil this svstciii was iloscrihcil 

 lirii'tly ill Aiii\ul<i.\ti>imt diioilinalr li.v tliat writi'r in l!ill."i. Later 

 (1!M0) (uildschiiiidt stmlicd tin' system in Axcaris liimhrirDidci 

 followed liy Martini (lUllil in (Kriiiiria iipii, ImmincI: (li'-l, 

 l!)2-i) in SIroiiiii/his rilentiilii.'i, de Hruyn (1!IH4) in Angiisli 

 carriim holoph mm, and vaiimis cdiservations l)y the writers 

 (1933, 1!IH7) refer to freeliviiiK ami jiarasitie forms. 



In substance, tliis system consists of tliree loiiKifiiiiina! 

 nerves, one situated near tlie center of each sector and extend 

 ing from the base nearly to the anterior end of the esophagus 

 ( Fiff. 97K). These nerves contain in their course a series of 

 nerve cells and two or three commissures .ioining the lonKi- 

 tudinal nerves. In most forms we find a conimisure at the 

 li.ase of the eoriius. another in the anterior ]iart of the Inilbar 

 region and a third in the jiosterior part of the bulbar region. 

 Nerve cell nuclei may usually be distinguished from the other 

 t.vpes of nuclei though the.v vary considerably in size, but in 

 smaller forms it is often not possible to identify all nuclei 

 with certaint.v. In such ca.ses one must place reliance purel.v 

 upon considerations based on comparative anatomy. In the 

 ma.jority of instances no attempt has been made to trace the 

 nerve fibers but the nerve cell pattern has been recorded and 

 found to be of considerable value from the standpoint of 

 comparative histology. In ver.v large nematodes the nerve 

 cells of the esophagus are often disproportionately small and 

 may easil.v be overlooked. This seems a probable reason for 

 the small number of such cells reported to occur in ascarids 

 and spiruroids. In forms with multinucleate esophageal 

 glands the nerve cells may be easily confused with gland 

 nuclei. Of course, it is also possible that in such forms 

 (always devoid of a valved bulb") there is no need for the 

 complicated esophago-synipathetic system of smaller forms. 



In Spironoura affine (i"'ig. 07A) there are seven cells in 

 each nerve anterior to the nerve ring (Fig. 97P) ; two of these 

 are glia cells (ni..,, nm-i'i), the remainder nerve cells (n,.i«'). 

 The nerve fibers give off lateral branches (Fig 97P) into the 

 radial muscle regions. No further nerve cells are present in 

 the proeorpus. The metacorpus contains three large nerve cells 

 in the dorsal nerve (n2<, a., .ni) and five nerve cells in each 

 subventral nerve (n22-M. -.-.n, -.a--.,,). At the base of the 

 metacorpus we find a well develojied commissure between nn.-.u 

 and 11:12-31. The bulbar region (Fig. S)7Q) contains nine cells 

 attributable to the nervous system of which at least two 

 (041-42) and possibly a third (nri«) are probably glia cells. 

 There are two commissures in the bulbar region, an anterior 

 and a posterior (Fig. 97A). The connection of the esophago- 

 sympathetic with the central nervous system has not been ob- 

 served for Spironoura. However, we presume it to be similar 

 to that of Ascaris in which a process of each of the subventral 

 nerves passes through the external wall of the esophagus near 

 the level of the dorsal gland orifice (Fig. 97R). This process 

 continues posteriorly on the outside of the esophagus connect- 

 ing with a bipolar cell and through this cell with the nerve 

 ring. 



Goldschmidt recorded only 17 cells in this .system in Ascaris 

 Iiimbricoidc.i in which Hsii recorded 18 cells; de Bruyn re- 

 corded 27 in Anffusticariim Imloptcrum and Martini 20 in 

 Oxyurin rqui. All of these writers mention cells of dubious or 

 unknown significance in the esophagus, particularly in the pro- 

 corpus. Our own observations on Ascaris Jiimbricoides indi- 

 cate that a set of si.x cells near the level of the dorsal gland 

 orifice are homologous to nj-o of Spironoura. 



The peculiar distribution of nerve cells in representatives 

 of the suborder Enoplina is worth.v of particular note since it 

 is very probably indicative of relationship. As ma.v be seen 

 from the diagrams (Fig. 90) niii-211 and n.a-.n are usuall.v 

 marginal in position in the subventral sectors as are nai-.n in 

 the dorsal sector. Together with n2t. and Um the h.tter nuclei 

 form a quadrangle in forms such as Tripi/la pnpiVata, Dorif- 

 laimus ohtjisicnudntns and MrioiychoJaimus prist innis. 



3. FINER STRUCTURE OF THE 

 ESOPHAGUS 



Fiber.';. — ronsiderable discussion has taken place as to 

 whether or not the marginal fibers are contractile. Haniann 

 (189.".), Rauther (1907), Allgen (1921), Plenk (1924, 1925, 

 1926) and Looss (190.1) maintained that the marginals are 

 contractile, while Looss (1890), Schneider (1902), Gold- 

 schmidt (1904) and Martini (191(i, 1922) hold that they are 

 supporting or skeletal structures and observations of the writ- 



ers support this view. In the inargin.il region of .Isruris 

 one finds two types of fibers, a first type, extending from the 

 esojihageal lining to the esophage:il covering, ;i .second type 

 extending limgitiKlinally in two more or less distinct rows, one 

 on each side of the esoidi;ige.il margin. This second type, the 

 "fiber plates" of Goldsohiiii<it (1904), is known only in 

 ascarids. 



The radial fibers extend more or less perpendicularly from 

 the esoiihagcal lining to the extern.'il covering of the esopha- 

 gus but often run rather obliipiely so that their contraction 

 might easily shorten the esophagus to a moderate extent. 

 K. <'. Schneider (1902) characterized the radial fibers as 

 striated muscle. This view was supporteii by Martini (191fi) 

 though other .■luthors including (ioldschinidt (1904) disagree, 

 stating that the appearance of striation is due to a minute 

 .system of su|iporting fibrils. Convincing evidence of striation 

 of the muscle is not yet established. It is therefore con- 

 cluded th;it if such is jiresent, it must be of a rather peculiar 

 character hardly comiiaiable to striated muscle in other or- 

 ganisms. 



Finally the "fenestrated membr;ine" described by Gold- 

 schmidt (1904), Kulmatycki (1918, 1922) and de' Bruyn 

 (1934) in ascarids shall be discu.s.sed. This is a longitudinal 

 membrane between the external and the internal coverings of 

 the esophagus beginning at some distance from the head, end- 

 ing near the ba.se of the esoidiagus. The writers find no indi- 

 cation of such a structure. However, Kulmatycki (1922) 

 states that it is actually double and in places can be seen to 

 be a distinct tube. He illustrates that which is obviously an 

 esophageal gland tubule. Since the gl;ind branches coincide 

 with the location of the "fenestrated membrane," and since 

 we can find no other structure fitting the description, the 

 whole probably is a misinterpretation. 



Ducts .\nd Tubules. — The internal structure of the 

 esophageal glands has been very little studied and a generali- 

 zation from the meager information available would be pre- 

 sumptuous. In the past the glands have been considered as 

 rather simple structures, most investigators regarding the ducts 

 as in direct continuity with the gland protoplasm. Actually, 

 this is never the case. The esophageal gland ducts are con- 

 tinuous with tubules of various types. When the gland orifice 

 is some distance from the actual beginning of the gland sub- 

 stance, there is a long unbranched central duct. This duct 

 ma.v continue after reaching the glandular region and give 

 off lateral paired side branches, "pinnate branching." The 

 terminations of the branches may be "tubular'' or "alveolar 

 (acinus)." 



Hsii (1933) speaks of "simple tubular" glands in Philo- 

 vietra and Draciiiu'iilus hoiidcmrri stating that other nematodes 

 have "branched tubular" glands. It is very easy to fall into 

 error regarding such structures, particularly when the glands 

 terminate in acini or branched acini. This is, in fact, the 

 case in regard to the glands of BracuncuJtis dahomrnsis, the 

 subventral ones being compound branched alveolar glands, 

 while the dorsal is apparentl.v of the simple branched alveidar 

 type. 



In forms such as Ascaris hnnhricoidcs the dorsal gland is 

 simple (piiinately branched); the suhventrals are coniiiimnd 

 (palmatel.v branched) and tubular. In Phi/.tahiplrra majillaris 

 all three glands are simple (pinnately branched) and appar- 

 ently tubular (Fig. 98H). However, one has difficulty in 

 tracing the secondary and tertiary tubules; the.v might easily 

 terminate in acini. The compound form of the dichotomously 

 branching tubular glands of dioctoph.vmoids is obvious, as are 

 the simple branched tubular glands of Trichiiris ovi.i and 

 Agamcriiiis dccaiidata (Fig. 96). 



Alveolar glands are particularl.v difficult to stud.v. Preser- 

 vation of the tubules in satisfactory condition for stud.v is 

 actually a rarit.v and for answer to many of the problems one 

 must look to living specimens. Quite often the lobulations 

 of the gland protoplasm itself are mistaken for the tubules. 

 Such lobulation is dependent upon muscle distribution and may 

 have no bearing on the tubular system (the stichocytes of 

 Trichiiris oris and Agamcrniis dccaiidala have branched tubules 

 though the glands are not highly lobulated). 



"('llKOMlDl-\."- Working with Ascaris liimhricnidcs Gold- 

 schmidt (1904) described bodies in the plasma of the muscles 

 associated with the radial nuclei. The.v stained intensely with 

 hematoxylin and he termed them chromidi;i. These bodies he 

 cimceived to be "vegetative" nuclei originating from the 

 radial nuclei. Vejdovsky (1907) and Bilek (1909) considered 

 them artefacts but Hirschler (1910, 1912) demonstrated their 

 existence in the living cell. Neither Hirschler, v(m Kemnitz 

 (1912) nor Kulmatycki (1922) found any evidence that they 

 originated from the nucleus. These bodies are found only in 



95 



